drm/radeon: use locked rmmap to remove sarea mapping.

this exports the locked version of the symbol as struct_mutex locks it all.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c
index 7fb690b..72c667f 100644
--- a/drivers/gpu/drm/drm_bufs.c
+++ b/drivers/gpu/drm/drm_bufs.c
@@ -440,6 +440,7 @@
 
 	return 0;
 }
+EXPORT_SYMBOL(drm_rmmap_locked);
 
 int drm_rmmap(struct drm_device *dev, drm_local_map_t *map)
 {