arm: imx: common rework cache settings for imx6

Rework cache settings for imx6, move cache configuration
to imx-common/cache.c so it can be reused for newer SoC

Signed-off-by: Adrian Alonso <aalonso@freescale.com>
diff --git a/arch/arm/imx-common/Makefile b/arch/arm/imx-common/Makefile
index b9f1ca4..3b034e1 100644
--- a/arch/arm/imx-common/Makefile
+++ b/arch/arm/imx-common/Makefile
@@ -19,6 +19,7 @@
 obj-$(CONFIG_SPL_BUILD)	+= spl.o
 endif
 ifeq ($(SOC),$(filter $(SOC),mx6))
+obj-y 	+= cache.o
 obj-$(CONFIG_CMD_SATA) += sata.o
 obj-$(CONFIG_IMX_VIDEO_SKIP) += video.o
 endif