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/ae350_rv64_xip_defconfig b/configs/ae350_rv64_xip_defconfig
index cb2b0f1..1b12b2f 100644
--- a/configs/ae350_rv64_xip_defconfig
+++ b/configs/ae350_rv64_xip_defconfig
@@ -7,6 +7,7 @@
 CONFIG_ARCH_RV64I=y
 CONFIG_XIP=y
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_LOAD_ADDR=0x100000
 CONFIG_FIT=y
 CONFIG_BOOTDELAY=3
 CONFIG_BOARD_EARLY_INIT_F=y