fs: update comments to point correct document

dcache-locking.txt is not exist any more, and the path was not
correct anyway. Fix it.
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

fs/dcache.c

@@ -1781,7 +1781,7 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
 	 * false-negative result. d_lookup() protects against concurrent
 	 * renames using rename_lock seqlock.
 	 *
-	 * See Documentation/vfs/dcache-locking.txt for more details.
+	 * See Documentation/filesystems/path-lookup.txt for more details.
 	 */
 	hlist_bl_for_each_entry_rcu(dentry, node, &b->head, d_hash) {
 		struct inode *i;
@@ -1901,7 +1901,7 @@ struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
 	 * false-negative result. d_lookup() protects against concurrent
 	 * renames using rename_lock seqlock.
 	 *
-	 * See Documentation/vfs/dcache-locking.txt for more details.
+	 * See Documentation/filesystems/path-lookup.txt for more details.
 	 */
 	rcu_read_lock();