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/tplink_wdr4300_defconfig b/configs/tplink_wdr4300_defconfig
index 849d332..04b40b1 100644
--- a/configs/tplink_wdr4300_defconfig
+++ b/configs/tplink_wdr4300_defconfig
@@ -7,6 +7,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="tplink_wdr4300"
 CONFIG_ARCH_ATH79=y
 CONFIG_BOARD_TPLINK_WDR4300=y
+CONFIG_SYS_LOAD_ADDR=0xa1000000
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/mtdblock2 rootfstype=squashfs"