drm/qxl: Don't set a gamma table size

qxl doesn't have any functions for setting the gamma table, so this is
completely defunct.

Not nice to lie to userspace, so let's stop!

Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1459331485-28376-10-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/qxl/qxl_display.c

@@ -730,7 +730,6 @@ static int qdev_crtc_init(struct drm_device *dev, int crtc_id)
 
 	drm_crtc_init(dev, &qxl_crtc->base, &qxl_crtc_funcs);
 	qxl_crtc->index = crtc_id;
-	drm_mode_crtc_set_gamma_size(&qxl_crtc->base, 256);
 	drm_crtc_helper_add(&qxl_crtc->base, &qxl_crtc_helper_funcs);
 	return 0;
 }