CHIP: add device tree overlay support

CHIP and CHIP Pro devices have options of DIP addon boards some of which need
overlays from the beginning so it makes sense to enable device tree overlays.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>

configs/CHIP_defconfig

@@ -24,3 +24,5 @@ CONFIG_USB_GADGET_DOWNLOAD=y
 CONFIG_G_DNL_MANUFACTURER="Allwinner Technology"
 CONFIG_G_DNL_VENDOR_NUM=0x1f3a
 CONFIG_G_DNL_PRODUCT_NUM=0x1010
+CONFIG_OF_LIBFDT=y
+CONFIG_OF_LIBFDT_OVERLAY=y

configs/CHIP_pro_defconfig

@@ -30,3 +30,5 @@ CONFIG_USB_GADGET_DOWNLOAD=y
 CONFIG_G_DNL_MANUFACTURER="Allwinner Technology"
 CONFIG_G_DNL_VENDOR_NUM=0x1f3a
 CONFIG_G_DNL_PRODUCT_NUM=0x1010
+CONFIG_OF_LIBFDT=y
+CONFIG_OF_LIBFDT_OVERLAY=y