configs: rockchip: imply OF_LIBFDT_OVERLAY for rk3308 and rk3328

for rk3308, all defconfigs have CONFIG_OF_LIBFDT_OVERLAY=y, so enable it
by default.

for rk3328, any defconfig doesn't have it. but there is no strong reason
not to enable it. at least it's required for ROCK Pi E.

Signed-off-by: FUKAUMI Naoki <naoki@radxa.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/Kconfig b/arch/arm/mach-rockchip/Kconfig
index 2242ed9..fc1b638 100644
--- a/arch/arm/mach-rockchip/Kconfig
+++ b/arch/arm/mach-rockchip/Kconfig
@@ -169,6 +169,7 @@
 	imply LEGACY_IMAGE_FORMAT
 	imply MISC
 	imply MISC_INIT_R
+	imply OF_LIBFDT_OVERLAY
 	imply OF_UPSTREAM
 	imply RNG_ROCKCHIP
 	imply ROCKCHIP_COMMON_BOARD
@@ -199,6 +200,7 @@
 	imply ARMV8_SET_SMPEN
 	imply MISC
 	imply MISC_INIT_R
+	imply OF_LIBFDT_OVERLAY
 	imply OF_LIVE
 	imply OF_UPSTREAM
 	imply PRE_CONSOLE_BUFFER