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/gardena-smart-gateway-mt7688_defconfig b/configs/gardena-smart-gateway-mt7688_defconfig
index 46b9849..73260b5 100644
--- a/configs/gardena-smart-gateway-mt7688_defconfig
+++ b/configs/gardena-smart-gateway-mt7688_defconfig
@@ -19,6 +19,7 @@
 # CONFIG_MIPS_BOOT_ENV_LEGACY is not set
 CONFIG_MIPS_BOOT_FDT=y
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
+CONFIG_SYS_LOAD_ADDR=0x80100000
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
 CONFIG_LEGACY_IMAGE_FORMAT=y