drm: Push dirtyfb ioctl kms locking down to drivers

Not all drivers will need take all the modeset locks for dirtyfb, so
push the locking down to the drivers.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/omapdrm/omap_fb.c b/drivers/gpu/drm/omapdrm/omap_fb.c
index f2b8f06..f466c4a 100644
--- a/drivers/gpu/drm/omapdrm/omap_fb.c
+++ b/drivers/gpu/drm/omapdrm/omap_fb.c
@@ -123,12 +123,16 @@
 {
 	int i;
 
+	drm_modeset_lock_all(fb->dev);
+
 	for (i = 0; i < num_clips; i++) {
 		omap_framebuffer_flush(fb, clips[i].x1, clips[i].y1,
 					clips[i].x2 - clips[i].x1,
 					clips[i].y2 - clips[i].y1);
 	}
 
+	drm_modeset_unlock_all(fb->dev);
+
 	return 0;
 }