[media] v4l2-dv-timings.h: add new 4K DMT resolutions

VESA added two new DMT timings in their latest standard document. Add these
to v4l2-dv-timings.h.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>