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/maltael_defconfig b/configs/maltael_defconfig
index 77c05d7..d9f580f 100644
--- a/configs/maltael_defconfig
+++ b/configs/maltael_defconfig
@@ -6,6 +6,7 @@
 CONFIG_TARGET_MALTA=y
 CONFIG_BUILD_TARGET="u-boot-swap.bin"
 CONFIG_SYS_LITTLE_ENDIAN=y
+CONFIG_SYS_LOAD_ADDR=0x81000000
 # CONFIG_AUTOBOOT is not set
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_MISC_INIT_R=y