[media] pvrusb2: convert to video_ioctl2

Note: there is one FIXME remaining: the tvnorms field of struct
video_device should be set up correctly. I have used V4L2_STD_ALL for
now, but I'm sure this can be improved. This field is used by
video_ioctl2 to implement ENUMSTD.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>