imx: add i.MX8QXP MEK board support

Add i.MX8QXP MEK board support
Enabled pinctrl/clk/power-domain/mmc/i2c/fec driver.
Added README file.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
diff --git a/arch/arm/mach-imx/imx8/Kconfig b/arch/arm/mach-imx/imx8/Kconfig
index 28910c1..0d3a87c 100644
--- a/arch/arm/mach-imx/imx8/Kconfig
+++ b/arch/arm/mach-imx/imx8/Kconfig
@@ -10,4 +10,17 @@
 config SYS_SOC
 	default "imx8"
 
+choice
+	prompt "i.MX8 board select"
+	optional
+
+config TARGET_IMX8QXP_MEK
+	bool "Support i.MX8QXP MEK board"
+	select BOARD_LATE_INIT
+	select IMX8QXP
+
+endchoice
+
+source "board/freescale/imx8qxp_mek/Kconfig"
+
 endif