Add a comment indicating that the locking protocol should be updated

to be 'L L L' for vop_getattr().  Don't update it yet, because there
are still many offenders.

sys/kern/vnode_if.src

@@ -152,6 +152,8 @@ vop_access {
 #
 #% getattr	vp	= = =
 #
+# XXX: This should be L L L
+#
 vop_getattr {
 	IN struct vnode *vp;
 	OUT struct vattr *vap;