cifs: don't spam the logs on unexpected lookup errors

Andrey reported that he was seeing cifs.ko spam the logs with messages
like this:

    CIFS VFS: Unexpected lookup error -26

He was listing the root directory of a server and hitting an error when
trying to QUERY_PATH_INFO against hiberfil.sys and pagefile.sys. The
right fix would be to switch the lookup code over to using FIND_FIRST,
but until then we really don't need to report this at a level of
KERN_ERR. Convert this message over to FYI level.

Reported-by: "Andrey Shernyukov" <andreysh@nioch.nsc.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/dir.c

@@ -756,7 +756,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 	/*	if it was once a directory (but how can we tell?) we could do
 		shrink_dcache_parent(direntry); */
 	} else if (rc != -EACCES) {
-		cifs_dbg(VFS, "Unexpected lookup error %d\n", rc);
+		cifs_dbg(FYI, "Unexpected lookup error %d\n", rc);
 		/* We special case check for Access Denied - since that
 		is a common return code */
 	}