Convert CONFIG_SYS_MEM_TOP_HIDE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MEM_TOP_HIDE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/s5pc210_universal_defconfig b/configs/s5pc210_universal_defconfig
index 8a34908..e70ce25 100644
--- a/configs/s5pc210_universal_defconfig
+++ b/configs/s5pc210_universal_defconfig
@@ -13,6 +13,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="exynos4210-universal_c210"
 CONFIG_SYS_LOAD_ADDR=0x44800000
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_MEM_TOP_HIDE=0x100000
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="Please use defined boot"
 CONFIG_BOOTCOMMAND="run mmcboot"