UPSTREAM: binderfs: rework binderfs_fill_super()

Al pointed out that on binderfs_fill_super() error
deactivate_locked_super() will call binderfs_kill_super() so all of the
freeing and putting we currently do in binderfs_fill_super() is unnecessary
and buggy. Let's simply return errors and let binderfs_fill_super() take
care of cleaning up on error.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christian Brauner <christian@brauner.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Bug: 136497735
(cherry picked from commit 36975fc3e5f241cc4f45df4ab4624d7d5199d9ed)
Change-Id: I89cac3746d67638901e554c3ede6c0f2931e67d4
Signed-off-by: Hridya Valsaraju <hridya@google.com>