[media] pvrusb2: fix g/s_tuner support

The tuner-core subdev requires that the type field of v4l2_tuner is
filled in correctly. This is done in v4l2-ioctl.c, but pvrusb2 doesn't
use that yet, so we have to do it manually based on whether the current
input is radio or not.

Tested with my pvrusb2.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Mike Isely <isely@pobox.com>
Cc: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>