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/sufile.c b/fs/nilfs2/sufile.c
index 37b9631..ce679cf 100644
--- a/fs/nilfs2/sufile.c
+++ b/fs/nilfs2/sufile.c
@@ -562,7 +562,7 @@
 {
 	struct buffer_head *header_bh;
 	struct nilfs_sufile_header *header;
-	struct the_nilfs *nilfs = NILFS_I_NILFS(sufile);
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
 	void *kaddr;
 	int ret;
 
@@ -812,7 +812,7 @@
 	struct nilfs_segment_usage *su;
 	struct nilfs_suinfo *si = buf;
 	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
-	struct the_nilfs *nilfs = NILFS_I_NILFS(sufile);
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
 	void *kaddr;
 	unsigned long nsegs, segusages_per_block;
 	ssize_t n;