xfs: add a xfs_dqhold helper

Factor the common pattern of:

	xfs_dqlock(dqp);
	XFS_DQHOLD(dqp);
	xfs_dqunlock(dqp);

into a new helper, and remove XFS_DQHOLD now that only one other caller
is left.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index f1d3ccb..2ce562c 100644
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -733,7 +733,7 @@
 			return -1;
 		}
 
-		XFS_DQHOLD(dqp);
+		dqp->q_nrefs++;
 
 		/*
 		 * move the dquot to the front of the hashchain