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/openrd_base_defconfig b/configs/openrd_base_defconfig
index 72d6358..54ba779 100644
--- a/configs/openrd_base_defconfig
+++ b/configs/openrd_base_defconfig
@@ -11,6 +11,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="kirkwood-openrd-base"
 CONFIG_IDENT_STRING="\nOpenRD-Base"
 # CONFIG_SYS_MALLOC_F is not set
+CONFIG_SYS_LOAD_ADDR=0x800000
 CONFIG_SYS_EXTRA_OPTIONS="BOARD_IS_OPENRD_BASE"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_PREBOOT=y