filesystems: add missing nlink wrappers

Replace direct i_nlink updates with the respective updater function
(inc_nlink, drop_nlink, clear_nlink, inode_dec_link_count).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/fs/hpfs/inode.c b/fs/hpfs/inode.c
index 338cd83..dfe800c 100644
--- a/fs/hpfs/inode.c
+++ b/fs/hpfs/inode.c
@@ -53,7 +53,7 @@
 		i->i_mode &= ~0111;
 		i->i_op = &hpfs_file_iops;
 		i->i_fop = &hpfs_file_ops;
-		i->i_nlink = 0;*/
+		clear_nlink(i);*/
 		make_bad_inode(i);
 		return;
 	}