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/bcm963158_ram_defconfig b/configs/bcm963158_ram_defconfig
index f7f1b35..f535b81 100644
--- a/configs/bcm963158_ram_defconfig
+++ b/configs/bcm963158_ram_defconfig
@@ -9,6 +9,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="bcm963158"
 CONFIG_TARGET_BCM963158=y
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
+CONFIG_SYS_LOAD_ADDR=0x10000000
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
 CONFIG_FIT_RSASSA_PSS=y