drm: Remove clock_index from struct drm_display_mode

This field was only accessed by the nouveau driver, but never set. So
concluded we can rid of this one.
Acked-by: NBen Skeggs <bskeggs@redhat.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/nouveau/dispnv04/crtc.c

@@ -326,8 +326,6 @@ nv_crtc_mode_set_vga(struct drm_crtc *crtc, struct drm_display_mode *mode)
 			regp->MiscOutReg = 0x23;	/* +hsync +vsync */
 	}
 
-	regp->MiscOutReg |= (mode->clock_index & 0x03) << 2;
-
 	/*
 	 * Time Sequencer
 	 */

include/drm/drm_crtc.h

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