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/logfs/inode.c b/fs/logfs/inode.c
index 9abb048..7e441ad 100644
--- a/fs/logfs/inode.c
+++ b/fs/logfs/inode.c
@@ -93,7 +93,7 @@
 		/* inode->i_nlink == 0 can be true when called from
 		 * block validator */
 		/* set i_nlink to 0 to prevent caching */
-		inode->i_nlink = 0;
+		clear_nlink(inode);
 		logfs_inode(inode)->li_flags |= LOGFS_IF_ZOMBIE;
 		iget_failed(inode);
 		if (!err)