nilfs2: get rid of NILFS_I_NILFS

This replaces all references of NILFS_I_NILFS(inode)->ns_bdev with
inode->i_sb->s_bdev and unfolds remaining uses of NILFS_I_NILFS inline
function.

Before 2.6.37, referring to a nilfs object from inodes needed a
conditional judgement, and NILFS_I_NILFS was helpful to simplify it.
But now we can simply do it by going through a super block instance
like inode->i_sb->s_fs_info.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/mdt.h b/fs/nilfs2/mdt.h
index ed68563..baea036 100644
--- a/fs/nilfs2/mdt.h
+++ b/fs/nilfs2/mdt.h
@@ -64,11 +64,6 @@
 	return inode->i_private;
 }
 
-static inline struct the_nilfs *NILFS_I_NILFS(struct inode *inode)
-{
-	return inode->i_sb->s_fs_info;
-}
-
 /* Default GFP flags using highmem */
 #define NILFS_MDT_GFP      (__GFP_WAIT | __GFP_IO | __GFP_HIGHMEM)
 
@@ -108,7 +103,7 @@
 
 static inline __u64 nilfs_mdt_cno(struct inode *inode)
 {
-	return NILFS_I_NILFS(inode)->ns_cno;
+	return ((struct the_nilfs *)inode->i_sb->s_fs_info)->ns_cno;
 }
 
 #define nilfs_mdt_bgl_lock(inode, bg) \