acct: get rid of acct_list

Put these suckers on per-vfsmount and per-superblock lists instead.
Note: right now it's still acct_lock for everything, but that's
going to change.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namespace.c

@@ -956,7 +956,7 @@ put_again:
 		mnt->mnt_pinned = 0;
 		rcu_read_unlock();
 		unlock_mount_hash();
-		acct_auto_close_mnt(&mnt->mnt);
+		acct_auto_close_mnt(&mnt->mnt_pins);
 		goto put_again;
 	}
 	if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {