net: ethernet: ti: cpsw: flower: validate control flags

This driver currently doesn't support any control flags.

Use flow_rule_match_has_control_flags() to check for control flags,
such as can be set through `tc flower ... ip_flags frag`.

In case any control flags are masked, flow_rule_match_has_control_flags()
sets a NL extended error message, and we return -EOPNOTSUPP.

Only compile-tested.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240422152656.175627-1-ast@fiberby.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/ti/cpsw_priv.c

@@ -1404,6 +1404,9 @@ static int cpsw_qos_clsflower_add_policer(struct cpsw_priv *priv,
 		return -EOPNOTSUPP;
 	}
 
+	if (flow_rule_match_has_control_flags(rule, extack))
+		return -EOPNOTSUPP;
+
 	if (!flow_rule_match_key(rule, FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
 		NL_SET_ERR_MSG_MOD(extack, "Not matching on eth address");
 		return -EOPNOTSUPP;