am437x: Add am437x_sk_evm_defconfig using CONFIG_DM

Import various DT files for am437x-sk-evm from Linux Kernel v4.2
Add config file for this board, enable DM, DM_GPIO, DM_SERIAL
and DM_MMC.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index c663973..23939b0 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -66,7 +66,7 @@
 	zynq-zc770-xm012.dtb \
 	zynq-zc770-xm013.dtb
 dtb-$(CONFIG_AM33XX) += am335x-boneblack.dtb am335x-evm.dtb
-dtb-$(CONFIG_AM43XX) += am437x-gp-evm.dtb
+dtb-$(CONFIG_AM43XX) += am437x-gp-evm.dtb am437x-sk-evm.dtb
 
 dtb-$(CONFIG_ARCH_SOCFPGA) +=				\
 	socfpga_arria5_socdk.dtb			\