cache: temporarily drop the assert that dvp != vp when adding an entry

Historically it was allowed for any names, but arguably should never be
even attempted. Allow it again since there is a release pending and
allowing it is bug-compatible with previous behavior.

Reported by:	otis

sys/kern/vfs_cache.c

@@ -2266,7 +2266,12 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
 	KASSERT(cnp->cn_namelen <= NAME_MAX,
 	    ("%s: passed len %ld exceeds NAME_MAX (%d)", __func__, cnp->cn_namelen,
 	    NAME_MAX));
+#ifdef notyet
+	/*
+	 * Not everything doing this is weeded out yet.
+	 */
 	VNPASS(dvp != vp, dvp);
+#endif
 	VNPASS(!VN_IS_DOOMED(dvp), dvp);
 	VNPASS(dvp->v_type != VNON, dvp);
 	if (vp != NULL) {