ti: keystone: Move away from CONFIG_SOC_KEYSTONE

We have individual SOC symbols for each keystone 2 platform.  Use the
existing CONFIG_ARCH_KEYSTONE rather than CONFIG_SOC_KEYSTONE to
encompass all of the keystone families.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index f322775..9e44817 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -929,7 +929,7 @@
 dtb-$(CONFIG_RZA1) += \
 	r7s72100-gr-peach-u-boot.dtb
 
-dtb-$(CONFIG_SOC_KEYSTONE) += keystone-k2hk-evm.dtb \
+dtb-$(CONFIG_ARCH_KEYSTONE) += keystone-k2hk-evm.dtb \
 	keystone-k2l-evm.dtb \
 	keystone-k2e-evm.dtb \
 	keystone-k2g-evm.dtb \