drm/i915: Fix HSW sync flags to use pipe config adjusted_mode

intel_ddi_enable_transcoder_func() picked the sync flags from crtc->mode
instead of the pipe config adjusted_mode. Fix the problem and hopefully
rid my HSW machine of the remaining pipe config warnings.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>