xfs: convert the per-mount dquot list to use list heads

Convert the dquot list on the filesytesm to use listhead
infrastructure rather than the roll-your-own in the quota code.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/quota/xfs_qm.h b/fs/xfs/quota/xfs_qm.h
index 495564b..91bd053 100644
--- a/fs/xfs/quota/xfs_qm.h
+++ b/fs/xfs/quota/xfs_qm.h
@@ -106,7 +106,9 @@
 typedef struct xfs_quotainfo {
 	xfs_inode_t	*qi_uquotaip;	 /* user quota inode */
 	xfs_inode_t	*qi_gquotaip;	 /* group quota inode */
-	xfs_dqlist_t	 qi_dqlist;	 /* all dquots in filesys */
+	struct list_head qi_dqlist;	 /* all dquots in filesys */
+	struct mutex	 qi_dqlist_lock;
+	int		 qi_dquots;
 	int		 qi_dqreclaims;	 /* a change here indicates
 					    a removal in the dqlist */
 	time_t		 qi_btimelimit;	 /* limit for blks timer */