Convert CONFIG_SYS_LOAD_ADDR to Kconfig

Now that we have consistent usage, migrate this symbol to Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/configs/mx53ppd_defconfig b/configs/mx53ppd_defconfig
index 4a8fa34..288a1dc 100644
--- a/configs/mx53ppd_defconfig
+++ b/configs/mx53ppd_defconfig
@@ -8,6 +8,7 @@
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="imx53-ppd"
 CONFIG_BOOTCOUNT_BOOTLIMIT=10
+CONFIG_SYS_LOAD_ADDR=0x72000000
 CONFIG_FIT=y
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_OF_BOARD_SETUP=y