arm: add support for SoC s5p4418 (cpu) / nanopi2 board

Changes in relation to FriendlyARM's U-Boot nanopi2-v2016.01:
- SPL not supported yet --> no spl-dir in arch/arm/cpu/armv7/s5p4418/.
  Appropriate line in Makefile removed.
- cpu.c: '#include <cpu_func.h>' added.
- arch/arm/cpu/armv7/s5p4418/u-boot.lds removed, is not required
  anylonger.
- "obj-$(CONFIG_ARCH_NEXELL) += s5p-common/" added to
  arch/arm/cpu/armv7/Makefile since s5p-common/pwm.c is used instead
  of drivers/pwm/pwm-nexell.c.
- s5p4418.dtsi: '#include "../../../include/generated/autoconf.h"'
  removed, is not necessary, error at out-of-tree building.
  '#ifdef CONFIG_CPU_NXP4330'-blocks (2x) removed. Some minor changes
  regarding mmc. 'u-boot,dm-pre-reloc' added to dp0 because of added
  DM_VIDEO support.
- board/s5p4418/ renamed to board/friendlyarm/
- All s5p4418-boards except nanopi2 removed because there is no
  possibility to test the other boards.
- Kconfig: Changes to have a structure like mach-bcm283x (RaspberryPi),
  e.g. "config ..." entries moved from/to other Kconfig.
- "CONFIG_" removed from several s5p4418/nanopi2 specific defines
  because the appropriate values do not need to be configurable.
- nanopi2/board.c: All getenv(), getenv_ulong(), setenv() and saveenv()
  renamed to env_get(), env_get_ulong(), env_set() and env_save(),
  respectively. MACH_TYPE_S5P4418 is not defined anymore, therefore
  appropriate code removed (not necessary for DT-kernels).
- nanopi2/onewire.c: All crc8() renamed to crc8_ow() because crc8() is
  already defined in lib/crc8.c (with different parameters).
- dts: "nexell,s5pxx18-i2c" used instead of "i2c-gpio", i2c0 and
  i2c1 added. gmac-, ehci- and dwc2otg-entries removed because the
  appropriate functionality is not supported yet. New mmc-property
  "mmcboost" added.
  s5p4418-pinctrl.dtsi: gmac-entries removed, mmc- and i2c-entries
  added.
- '#ifdef CONFIG...' changed to 'if (IS_ENABLED(CONFIG...))' where
  possible (and similar).

Signed-off-by: Stefan Bosch <stefan_b@posteo.net>
diff --git a/arch/arm/dts/s5p4418-pinctrl.dtsi b/arch/arm/dts/s5p4418-pinctrl.dtsi
new file mode 100644
index 0000000..a7e1c2c
--- /dev/null
+++ b/arch/arm/dts/s5p4418-pinctrl.dtsi
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Nexell's s5p6818 SoC pin-mux and pin-config device tree source
+ *
+ * (C) Copyright 2020 Stefan Bosch <stefan_b@posteo.net>
+ *
+ * Copyright (C) 2016  Nexell Co., Ltd.
+ *		http://www.nexell.co.kr
+ *
+ * Nexell's s5p6818 SoC pin-mux and pin-config options are listed as
+ * device tree nodes in this file.
+ */
+
+pinctrl@C0010000 {
+	/*
+	 * values for "pin-pull":
+	 *	pulldown resistor = 0
+	 *	pullup = 1
+	 *	no pullup/down = 2
+	 */
+
+	/* MMC */
+	mmc0_clk: mmc0-clk {
+		pins = "gpioa-29";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <2>;
+	};
+
+	mmc0_cmd: mmc0-cmd {
+		pins = "gpioa-31";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <1>;
+	};
+
+	mmc0_bus4: mmc0-bus-width4 {
+		pins = "gpiob-1, gpiob-3, gpiob-5, gpiob-7";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <1>;
+	};
+
+	mmc1_clk: mmc1-clk {
+		pins = "gpiod-22";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <2>;
+	};
+
+	mmc1_cmd: mmc1-cmd {
+		pins = "gpiod-23";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <1>;
+	};
+
+	mmc1_bus4: mmc1-bus-width4 {
+		pins = "gpiod-24, gpiod-25, gpiod-26, gpiod-27";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <1>;
+	};
+
+	mmc2_clk: mmc2-clk {
+		pins = "gpioc-18";
+		pin-function = <2>;
+		pin-pull = <2>;
+		pin-strength = <2>;
+	};
+
+	mmc2_cmd: mmc2-cmd {
+		pins = "gpioc-19";
+		pin-function = <2>;
+		pin-pull = <2>;
+		pin-strength = <1>;
+	};
+
+	mmc2_bus4: mmc2-bus-width4 {
+		pins = "gpioc-20, gpioc-21, gpioc-22, gpioc-23";
+		pin-function = <2>;
+		pin-pull = <2>;
+		pin-strength = <1>;
+	};
+
+	mmc2_bus8: mmc2-bus-width8 {
+		nexell,pins = "gpioe-21", "gpioe-22", "gpioe-23", "gpioe-24";
+		pin-function = <2>;
+		pin-pull = <2>;
+		pin-strength = <1>;
+	};
+
+	/* I2C */
+	i2c0_sda:i2c0-sda {
+		pins = "gpiod-3";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <0>;
+	};
+
+	i2c0_scl:i2c0-scl {
+		pins = "gpiod-2";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <0>;
+	};
+
+	i2c1_sda:i2c1-sda {
+		pins = "gpiod-5";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <0>;
+	};
+
+	i2c1_scl:i2c1-scl {
+		pins = "gpiod-4";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <0>;
+	};
+
+	i2c2_sda:i2c2-sda {
+		pins = "gpiod-7";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <0>;
+	};
+
+	i2c2_scl:i2c2-scl {
+		pins = "gpiod-6";
+		pin-function = <1>;
+		pin-pull = <2>;
+		pin-strength = <0>;
+	};
+};