imx: Add i.MX8MM EVK board support.

Add board and SoC dts
Add ddr training code
support SD/MMC/GPIO/PINCTRL/UART

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/dts/imx8mm-evk-u-boot.dtsi b/arch/arm/dts/imx8mm-evk-u-boot.dtsi
new file mode 100644
index 0000000..1095d36
--- /dev/null
+++ b/arch/arm/dts/imx8mm-evk-u-boot.dtsi
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2019 NXP
+ */
+
+&{/soc} {
+	u-boot,dm-pre-reloc;
+	u-boot,dm-spl;
+};
+
+&clk {
+	u-boot,dm-spl;
+	u-boot,dm-pre-reloc;
+};
+
+&osc_24m {
+	u-boot,dm-spl;
+	u-boot,dm-pre-reloc;
+};
+
+&aips1 {
+	u-boot,dm-spl;
+	u-boot,dm-pre-reloc;
+};
+
+&aips2 {
+	u-boot,dm-spl;
+};
+
+&aips3 {
+	u-boot,dm-spl;
+};
+
+&iomuxc {
+	u-boot,dm-spl;
+};
+
+&pinctrl_reg_usdhc2_vmmc {
+	u-boot,dm-spl;
+};
+
+&pinctrl_uart2 {
+	u-boot,dm-spl;
+};
+
+&pinctrl_usdhc2_gpio {
+	u-boot,dm-spl;
+};
+
+&pinctrl_usdhc2 {
+	u-boot,dm-spl;
+};
+
+&pinctrl_usdhc3 {
+	u-boot,dm-spl;
+};
+
+&gpio1 {
+	u-boot,dm-spl;
+};
+
+&gpio2 {
+	u-boot,dm-spl;
+};
+
+&gpio3 {
+	u-boot,dm-spl;
+};
+
+&gpio4 {
+	u-boot,dm-spl;
+};
+
+&gpio5 {
+	u-boot,dm-spl;
+};
+
+&uart2 {
+	u-boot,dm-spl;
+};
+
+&usdhc1 {
+	u-boot,dm-spl;
+};
+
+&usdhc2 {
+	u-boot,dm-spl;
+};
+
+&usdhc3 {
+	u-boot,dm-spl;
+};