uwb: use uwb_rsv_callback instead of calling rsv->callback directly

Use uwb_rsv_callback wrapper instead of calling rsv->callback directly.
uwb_rsv_callback checks for NULL and is used by other callers of the
callback routine.
Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uwb/rsv.c

@@ -919,7 +919,7 @@ static void uwb_rsv_alien_bp_work(struct work_struct *work)
 
 	list_for_each_entry(rsv, &rc->reservations, rc_node) {
 		if (rsv->type != UWB_DRP_TYPE_ALIEN_BP) {
-			rsv->callback(rsv);
+			uwb_rsv_callback(rsv);
 		}
 	}