Fill in the std field from the video_device tvnorms field.

This fixes a v4l2-compliance failure.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NRob Taylor <rob.taylor@codethink.co.uk>
Acked-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>