net: sched: use PTR_ERR_OR_ZERO macro in tcf_block_cb_register

This line makes up what macro PTR_ERR_OR_ZERO already does. So,
make use of PTR_ERR_OR_ZERO rather than an open-code version.

This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_api.c

@@ -818,7 +818,7 @@ int tcf_block_cb_register(struct tcf_block *block,
 
 	block_cb = __tcf_block_cb_register(block, cb, cb_ident, cb_priv,
 					   extack);
-	return IS_ERR(block_cb) ? PTR_ERR(block_cb) : 0;
+	return PTR_ERR_OR_ZERO(block_cb);
 }
 EXPORT_SYMBOL(tcf_block_cb_register);