[media] adv7604: Don't ignore pad number in subdev DV timings pad operations

The dv_timings_cap() and enum_dv_timings() pad operations take a pad
number as an input argument and return the DV timings capabilities and
list of supported DV timings for that pad.

Commit bd3e275f ("[media] media: i2c: adv7604: Use v4l2-dv-timings
helpers") broke this as it started ignoring the pad number, always
returning the information associated with the currently selected input.
Fix it.

Fixes: bd3e275f ("[media] media: i2c: adv7604: Use v4l2-dv-timings helpers")

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: <stable@vger.kernel.org>      # for v4.6
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>