xfs: Replace macro XFS_DQ_TO_QIP with a function

In preparation for combined pquota/gquota support, for the sake
of readability, change the macro to an inline function.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_qm.h b/fs/xfs/xfs_qm.h
index 96568c2..051e43a 100644
--- a/fs/xfs/xfs_qm.h
+++ b/fs/xfs/xfs_qm.h
@@ -85,6 +85,22 @@
 	}
 	return NULL;
 }
+
+static inline struct xfs_inode *
+xfs_dq_to_quota_inode(struct xfs_dquot *dqp)
+{
+	switch (dqp->dq_flags & XFS_DQ_ALLTYPES) {
+	case XFS_DQ_USER:
+		return dqp->q_mount->m_quotainfo->qi_uquotaip;
+	case XFS_DQ_GROUP:
+	case XFS_DQ_PROJ:
+		return dqp->q_mount->m_quotainfo->qi_gquotaip;
+	default:
+		ASSERT(0);
+	}
+	return NULL;
+}
+
 extern int	xfs_qm_calc_dquots_per_chunk(struct xfs_mount *mp,
 					     unsigned int nbblks);
 extern void	xfs_trans_mod_dquot(xfs_trans_t *, xfs_dquot_t *, uint, long);