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/brppt1_nand_defconfig b/configs/brppt1_nand_defconfig
index 5bd5845..1db660f 100644
--- a/configs/brppt1_nand_defconfig
+++ b/configs/brppt1_nand_defconfig
@@ -14,6 +14,7 @@
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_SPL=y
 # CONFIG_EXPERT is not set
+CONFIG_SYS_LOAD_ADDR=0x80000000
 # CONFIG_FIT is not set
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_BOOTDELAY=0