[media] soc_camera: fix enum_input

Fill in the std field from the video_device tvnorms field.

This fixes a v4l2-compliance failure.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Rob Taylor <rob.taylor@codethink.co.uk>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>