drm: Remove synth_clock from struct drm_display_mode

This field is unused. Garbage collect it.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

include/drm/drm_crtc.h

@@ -156,7 +156,6 @@ struct drm_display_mode {
 	int height_mm;
 
 	/* Actual mode we give to hw */
-	int synth_clock;
 	int crtc_hdisplay;
 	int crtc_hblank_start;
 	int crtc_hblank_end;