[media] s5p-tv: add dv_timings support for hdmiphy

This just adds dv_timings support without modifying existing dv_preset
support, although I had to refactor a little bit in order to share
hdmiphy_find_conf() between the preset and timings code.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Acked-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>