[media] s5p-tv: hdmiphy: Add pad-level DV timings operations

The video enum_dv_timings operation is deprecated. Implement the
pad-level version of the operation to prepare for the removal of the
video version.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>