Convert CONFIG_SYS_CACHE_STASHING to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_CACHE_STASHING

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/kmcent2_defconfig b/configs/kmcent2_defconfig
index ee900f5..a0c9244 100644
--- a/configs/kmcent2_defconfig
+++ b/configs/kmcent2_defconfig
@@ -13,6 +13,7 @@
 CONFIG_ENABLE_36BIT_PHYS=y
 CONFIG_SYS_BOOK3E_HV=y
 CONFIG_SYS_FSL_CPC=y
+CONFIG_SYS_CACHE_STASHING=y
 # CONFIG_DEEP_SLEEP is not set
 CONFIG_PCIE1=y
 CONFIG_KM_DEF_NETDEV="eth2"