drm/omap: HDMI5: Use pointer to cfg->v_fc_config.timings in hdmi_core_video_config

By using a pointer to the omap_mode_timings struct we can unwrap lines to
make the code easier to follow.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>