OMAPDSS: fix timings for VENC to match what omapdrm expects

Otherwise check_timings fails and we get a "has no modes" message
from xrandr.

This fix makes the venc assume PAL and NTSC timings that match the
timings synthetized by copy_timings_drm_to_omap() from omapdrm
mode settings so that check_timings() succeeds.

Tested on: BeagleBoard XM, GTA04 and OpenPandora

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>