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/bcm7445_defconfig b/configs/bcm7445_defconfig
index 96e8da0..faff470 100644
--- a/configs/bcm7445_defconfig
+++ b/configs/bcm7445_defconfig
@@ -7,6 +7,7 @@
 CONFIG_ENV_OFFSET=0x1E0000
 CONFIG_ENV_SECT_SIZE=0x10000
 CONFIG_ENV_OFFSET_REDUND=0x1F0000
+CONFIG_SYS_LOAD_ADDR=0x02000000
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
 CONFIG_BOOTDELAY=1