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/vexpress_aemv8a_semi_defconfig b/configs/vexpress_aemv8a_semi_defconfig
index 2ecb776..787e0ac 100644
--- a/configs/vexpress_aemv8a_semi_defconfig
+++ b/configs/vexpress_aemv8a_semi_defconfig
@@ -9,6 +9,7 @@
 CONFIG_ENV_SECT_SIZE=0x40000
 CONFIG_IDENT_STRING=" vexpress_aemv8a"
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_LOAD_ADDR=0x90000000
 CONFIG_ANDROID_BOOT_IMAGE=y
 CONFIG_BOOTDELAY=1
 CONFIG_USE_BOOTARGS=y