drm: Make vblank_inmodeset unsigned

vblank_inmodeset is a bitmask, with only two bits mind you, but better
make it unsigned anyway.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

include/drm/drmP.h

@@ -1163,7 +1163,7 @@ struct drm_device {
 					/* for wraparound handling */
 	int *vblank_enabled;            /* so we don't call enable more than
 					   once per disable */
-	int *vblank_inmodeset;          /* Display driver is setting mode */
+	unsigned int *vblank_inmodeset; /* Display driver is setting mode */
 	u32 *last_vblank_wait;		/* Last vblank seqno waited per CRTC */
 	struct timer_list vblank_disable_timer;