vfs: Remove useless loop in mntput_no_expire

vfs: Remove useless loop in mntput_no_expire

Remove the extra reference added to mnt_count by the mnt_pinned code,
and stop jumping to the top of mntput_no_expire.

When fput synchronously called mntput that extra reference count and
the loop ensured that after acct_auto_close_mnt closed all of the
pinned references mntput_no_expire would then proceed actually
unmount the filesystem.

As fput is asynchronous today there is no point in looping.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>