configs: rockchip: rk3308: enable CONFIG_OF_LIBFDT_OVERLAY

enable CONFIG_OF_LIBFDT_OVERLAY and use it on Radxa ROCK Pi S.

Signed-off-by: FUKAUMI Naoki <naoki@radxa.com>
diff --git a/include/configs/rk3308_common.h b/include/configs/rk3308_common.h
index a413af1..861154f 100644
--- a/include/configs/rk3308_common.h
+++ b/include/configs/rk3308_common.h
@@ -17,6 +17,7 @@
 	"scriptaddr=0x00500000\0" \
 	"pxefile_addr_r=0x00600000\0" \
 	"fdt_addr_r=0x03e00000\0" \
+	"fdtoverlay_addr_r=0x03f00000\0" \
 	"kernel_addr_r=0x00680000\0" \
 	"ramdisk_addr_r=0x04000000\0"