glamor: xv: UYVY produces broken output

From gstreamer/gstreamer#3656 (closed): Running the following on Xwayland

$ gst-launch-1.0 videotestsrc ! video/x-raw,format=UYVY ! xvimagesink

produces broken output:

while

gst-launch-1.0 videotestsrc ! video/x-raw,format=UYVY ! glimagesink

and

$ gst-launch-1.0 videotestsrc ! video/x-raw,format=NV12 ! xvimagesink

works correctly:

suggesting an issue with the shader. The format was implemented relatively recently in !1164 (merged).