V4L/DVB (5272): Add V4L2_CAP_VIDEO_OUTPUT_POS capability

Add V4L2_CAP_VIDEO_OUTPUT_POS capability and x, y position coordinates
to struct v4l2_pix_format.
This is needed to support positioning the MPEG/YUV output of the cx23415.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>