nilfs2: get rid of mi_nilfs back pointer to nilfs object

This removes a back pointer to nilfs object from nilfs_mdt_info
structure that is attached to metadata files.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/sufile.h b/fs/nilfs2/sufile.h
index 203f610..a943fba 100644
--- a/fs/nilfs2/sufile.h
+++ b/fs/nilfs2/sufile.h
@@ -31,7 +31,7 @@
 
 static inline unsigned long nilfs_sufile_get_nsegments(struct inode *sufile)
 {
-	return NILFS_MDT(sufile)->mi_nilfs->ns_nsegments;
+	return NILFS_I_NILFS(sufile)->ns_nsegments;
 }
 
 unsigned long nilfs_sufile_get_ncleansegs(struct inode *sufile);