BKL: Remove BKL from ext3_put_super() and ext3_remount()

The BKL lock is protecting the remounting against a potential call to
ext3_put_super(). This could not happen, since this is protected by the
s_umount rw semaphore of struct super_block.

Therefore I think the BKL is protecting nothing here.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>