Convert CONFIG_SYS_UNIFY_CACHE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_UNIFY_CACHE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/M53017EVB_defconfig b/configs/M53017EVB_defconfig
index 901a15d..cec2520 100644
--- a/configs/M53017EVB_defconfig
+++ b/configs/M53017EVB_defconfig
@@ -42,6 +42,7 @@
 CONFIG_SYS_FLASH_CFI=y
 CONFIG_DM_ETH=y
 CONFIG_MCFFEC=y
+CONFIG_SYS_UNIFY_CACHE=y
 CONFIG_MII=y
 CONFIG_MCFRTC=y
 CONFIG_SYS_MCFRTC_BASE=0xFC0A8000