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/libfs.c b/fs/libfs.c
index a2c0029..f6d411e 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -490,7 +490,7 @@
 	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 	inode->i_op = &simple_dir_inode_operations;
 	inode->i_fop = &simple_dir_operations;
-	inode->i_nlink = 2;
+	set_nlink(inode, 2);
 	root = d_alloc_root(inode);
 	if (!root) {
 		iput(inode);