xfs: fix double IRELE in xfs_dqrele_inode

xfs_dqrele_inode calls xfs_iput to release the ilock and a reference
and then also calls IRELE which does a second decrement of the reference
count.  This leads to a premature freeing of inodes when quotas were turned
off while the filesystem was mounted.

Thanks to Utako Kusaka for reporting the bug and provinding a good testcase.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Utako Kusaka <u-kusaka@wm.jp.nec.com>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/quota/xfs_qm_syscalls.c

@@ -876,7 +876,6 @@ xfs_dqrele_inode(
 		ip->i_gdquot = NULL;
 	}
 	xfs_iput(ip, XFS_ILOCK_EXCL);
-	IRELE(ip);
 
 	return 0;
 }