filesystems: add set_nlink()

Replace remaining direct i_nlink updates with a new set_nlink()
updater function.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 786639f..0618aa3 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -1030,7 +1030,7 @@
 	}
 	btrfs_release_path(path);
 	if (nlink != inode->i_nlink) {
-		inode->i_nlink = nlink;
+		set_nlink(inode, nlink);
 		btrfs_update_inode(trans, root, inode);
 	}
 	BTRFS_I(inode)->index_cnt = (u64)-1;