drm/omap: Store CRTC timings in .set_timings() operation

The video timings are stored in the CRTC structure by the
omap_crtc_dss_set_timings() function, called by dss_mgr_set_timings()
from the .enable() operation of the internal encoders. This instead
belongs to the .set_timings() code paths. Move the
omap_crtc_dss_set_timings() calls accordingly.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>