keystone2: Move target selection to Kconfig

The config option TARGET_K2x_EVM is set by the k2x defconfigs to pick
a board target, but the header configs also set K2x_EVM. This config
is redundant, remove it and use TARGET_K2x_EVM everywhere in its place.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/arch/arm/mach-keystone/Makefile b/arch/arm/mach-keystone/Makefile
index b2ffe5b..8253a3b 100644
--- a/arch/arm/mach-keystone/Makefile
+++ b/arch/arm/mach-keystone/Makefile
@@ -18,5 +18,5 @@
 obj-y	+= msmc.o
 obj-y	+= ddr3.o
 obj-y	+= keystone.o
-obj-$(CONFIG_K2E_EVM) += ddr3_spd.o
-obj-$(CONFIG_K2HK_EVM) += ddr3_spd.o
+obj-$(CONFIG_TARGET_K2E_EVM) += ddr3_spd.o
+obj-$(CONFIG_TARGET_K2HK_EVM) += ddr3_spd.o