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/board/freescale/imx8mm_evk/MAINTAINERS b/board/freescale/imx8mm_evk/MAINTAINERS
new file mode 100644
index 0000000..b031bb0
--- /dev/null
+++ b/board/freescale/imx8mm_evk/MAINTAINERS
@@ -0,0 +1,6 @@
+i.MX8MM EVK BOARD
+M:	Peng Fan <peng.fan@nxp.com>
+S:	Maintained
+F:	board/freescale/imx8mm_evk/
+F:	include/configs/imx8mm_evk.h
+F:	configs/imx8mm_evk_defconfig