drm/i915/sdvo: Fully translate sync flags in the dtd->mode conversion

Instead of just a flag bit for each of the positive/negative sync
modes drm actually uses a separate flag for each ... This upsets the
modeset checker since the adjusted mode filled out at modeset time
doesn't match the one reconstructed at check time (since the
->get_config callback already gets this right).

Reported-by: Knut Petersen <Knut_Petersen@t-online.de>
Cc: Knut Petersen <Knut_Petersen@t-online.de>
References: http://www.gossamer-threads.com/lists/linux/kernel/1778688?do=post_view_threaded
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>