rygel: fix UI build

Add a patch to avoid failing on a configure error if UI example can't be
built if libgtk3 is available but not gst1-plugins-base (gstreamer-video
is only needed for UI example, not for rygel UI)

Fixes:
 - http://autobuild.buildroot.net/results/6c659aadfc418c0a27a93284eb34d75e2b0dc169



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>