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/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index baa82f8..481f4f7 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -108,7 +108,7 @@
 		ret->i_gid = hypfs_info->gid;
 		ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
 		if (mode & S_IFDIR)
-			ret->i_nlink = 2;
+			set_nlink(ret, 2);
 	}
 	return ret;
 }