drm: Remove unused drm_crtc->fb

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>

include/drm/drm_crtc.h

@@ -311,9 +311,6 @@ struct drm_crtc {
 	struct drm_plane *primary;
 	struct drm_plane *cursor;
 
-	/* framebuffer the connector is currently bound to */
-	struct drm_framebuffer *fb;
-
 	/* Temporary tracking of the old fb while a modeset is ongoing. Used
 	 * by drm_mode_set_config_internal to implement correct refcounting. */
 	struct drm_framebuffer *old_fb;