net: dsa: felix: 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>
Link: https://lore.kernel.org/r/20240417144407.104241-1-ast@fiberby.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/ocelot/felix_vsc9959.c

@@ -1755,6 +1755,9 @@ static int vsc9959_stream_identify(struct flow_cls_offload *f,
 	      BIT_ULL(FLOW_DISSECTOR_KEY_ETH_ADDRS)))
 		return -EOPNOTSUPP;
 
+	if (flow_rule_match_has_control_flags(rule, f->common.extack))
+		return -EOPNOTSUPP;
+
 	if (flow_rule_match_key(rule, FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
 		struct flow_match_eth_addrs match;