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/libretech-ac_defconfig b/configs/libretech-ac_defconfig
index c494b58..fa4427a 100644
--- a/configs/libretech-ac_defconfig
+++ b/configs/libretech-ac_defconfig
@@ -13,6 +13,7 @@
 CONFIG_DEBUG_UART_CLOCK=24000000
 CONFIG_IDENT_STRING=" libretech-ac"
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x1000000
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_USE_PREBOOT=y
 # CONFIG_DISPLAY_CPUINFO is not set