ARM: rmobile: Enable DTO support on Gen3

Enable support for applying DT overlays on Gen3. This is convenient
for handling extra additional hardware, like ie. the Kingfisher.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/configs/r8a7796_ulcb_defconfig b/configs/r8a7796_ulcb_defconfig
index cee34b3..1ac460b 100644
--- a/configs/r8a7796_ulcb_defconfig
+++ b/configs/r8a7796_ulcb_defconfig
@@ -56,4 +56,5 @@
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_EHCI_GENERIC=y
 CONFIG_USB_STORAGE=y
+CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_SMBIOS_MANUFACTURER=""