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/brxre1_defconfig b/configs/brxre1_defconfig
index bc8c5db..b98755e 100644
--- a/configs/brxre1_defconfig
+++ b/configs/brxre1_defconfig
@@ -17,6 +17,7 @@
 CONFIG_SPL=y
 CONFIG_ENV_OFFSET_REDUND=0x50000
 # CONFIG_EXPERT is not set
+CONFIG_SYS_LOAD_ADDR=0x80000000
 # CONFIG_FIT is not set
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_BOOTDELAY=0