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/dts/Makefile b/arch/arm/dts/Makefile
index 44ebc50..61598bd 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -452,6 +452,8 @@
 
 dtb-$(CONFIG_ARCH_MX7ULP) += imx7ulp-evk.dtb
 
+dtb-$(CONFIG_ARCH_IMX8) += fsl-imx8qxp-mek.dtb
+
 dtb-$(CONFIG_RCAR_GEN3) += \
 	r8a7795-h3ulcb.dtb \
 	r8a7795-salvator-x.dtb \