mips: Add LinkIt Smart 7688 support

The LinkIt Smart 7688 modules have a MT7688 SoC with 128 MiB of RAM
and 32 MiB of flash (SPI NOR).

This patch also includes 2 targets. One is the target that can be
programmed into the SPI NOR flash and a 2nd target "xxx-ram" is
added to support loading and booting via an already running U-Boot
version. This allows easy development and testing without the
need to flash the image each time.

Signed-off-by: Stefan Roese <sr@denx.de>
[fixed and regenerated defconfig files]
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/configs/linkit-smart-7688_defconfig b/configs/linkit-smart-7688_defconfig
new file mode 100644
index 0000000..62cdda1
--- /dev/null
+++ b/configs/linkit-smart-7688_defconfig
@@ -0,0 +1,55 @@
+CONFIG_MIPS=y
+CONFIG_SYS_TEXT_BASE=0x9c000000
+CONFIG_ARCH_MT7620=y
+CONFIG_BOOT_ROM=y
+CONFIG_ONBOARD_DDR2_SIZE_1024MBIT=y
+CONFIG_ONBOARD_DDR2_CHIP_WIDTH_16BIT=y
+# CONFIG_MIPS_BOOT_CMDLINE_LEGACY is not set
+# CONFIG_MIPS_BOOT_ENV_LEGACY is not set
+CONFIG_MIPS_BOOT_FDT=y
+CONFIG_NR_DRAM_BANKS=1
+# CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_OF_STDOUT_VIA_ALIAS=y
+CONFIG_SYS_CONSOLE_INFO_QUIET=y
+CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_HUSH_PARSER=y
+CONFIG_CMD_CPU=y
+CONFIG_CMD_LICENSE=y
+# CONFIG_CMD_BOOTD is not set
+# CONFIG_CMD_ELF is not set
+# CONFIG_CMD_XIMG is not set
+# CONFIG_CMD_CRC32 is not set
+CONFIG_CMD_MEMINFO=y
+# CONFIG_CMD_FLASH is not set
+# CONFIG_CMD_LOADS is not set
+CONFIG_CMD_SF=y
+CONFIG_CMD_SPI=y
+# CONFIG_CMD_NET is not set
+CONFIG_CMD_TIME=y
+CONFIG_OF_EMBED=y
+CONFIG_DEFAULT_DEVICE_TREE="linkit-smart-7688"
+CONFIG_ENV_IS_IN_SPI_FLASH=y
+# CONFIG_DM_DEVICE_REMOVE is not set
+CONFIG_HAVE_BLOCK_DEVICE=y
+CONFIG_CLK=y
+CONFIG_CPU=y
+CONFIG_DM_GPIO=y
+CONFIG_LED=y
+CONFIG_LED_BLINK=y
+CONFIG_LED_GPIO=y
+CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_GIGADEVICE=y
+CONFIG_SPI_FLASH_MACRONIX=y
+CONFIG_SPI_FLASH_SPANSION=y
+CONFIG_SPI_FLASH_STMICRO=y
+CONFIG_SPI_FLASH_WINBOND=y
+CONFIG_SPI_FLASH_MTD=y
+CONFIG_PHY=y
+CONFIG_POWER_DOMAIN=y
+CONFIG_RAM=y
+CONFIG_DM_RESET=y
+CONFIG_BAUDRATE=57600
+# CONFIG_SPL_SERIAL_PRESENT is not set
+CONFIG_SYS_NS16550=y
+CONFIG_SPI=y
+CONFIG_SYSRESET_SYSCON=y