Revert "loop: Fix double mutex_unlock(&loop_ctl_mutex) in loop_control_ioctl()"

Revert "loop: Fix double mutex_unlock(&loop_ctl_mutex) in loop_control_ioctl()"

This reverts commit d2762edcb6af99fc9322bab0b1d4e71a427760e8 which is
commit 628bd85947091830a8c4872adfd5ed1d515a9cf2 upstream.

It does not work properly in the 4.14.y tree and causes more problems
than it fixes, so revert it.

Reported-by: Thomas Lindroth <thomas.lindroth@gmail.com>
Reported-by: Jan Kara <jack@suse.cz>
Cc: syzbot <syzbot+c0138741c2290fc5e63f@syzkaller.appspotmail.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>