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/stack.c b/fs/stack.c
index b4f2ab48..9c11519 100644
--- a/fs/stack.c
+++ b/fs/stack.c
@@ -71,6 +71,6 @@
 	dest->i_ctime = src->i_ctime;
 	dest->i_blkbits = src->i_blkbits;
 	dest->i_flags = src->i_flags;
-	dest->i_nlink = src->i_nlink;
+	set_nlink(dest, src->i_nlink);
 }
 EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);