CEA-861-F tells us:
"When transmitting any RGB colorimetry, the Source should set the
 YQ-field to match the RGB Quantization Range being transmitted
 (e.g., when Limited Range RGB, set YQ=0 or when Full Range RGB,
 set YQ=1) and the Sink shall ignore the YQ-field."

So let's go ahead and do that. Perhaps there are sinks that don't
ignore the YQ as they should for RGB?

I wasn't able to find similar text in CEA-861-E, so it would seem
to be a fairly "recent" addition.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170111125725.8086-6-ville.syrjala@linux.intel.comReviewed-by: NJani Nikula <jani.nikula@intel.com>
Acked-by: NEric Anholt <eric@anholt.net>