bpf/flow_dissector: don't adjust nhoff by ETH_HLEN in BPF_PROG_TEST_RUN

Now that we use skb-less flow dissector let's return true nhoff and
thoff. We used to adjust them by ETH_HLEN because that's how it was
done in the skb case. For VLAN tests that looks confusing: nhoff is
pointing to vlan parts :-\

Warning, this is an API change for BPF_PROG_TEST_RUN! Feel free to drop
if you think that it's too late at this point to fix it.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

net/bpf/test_run.c

@@ -418,9 +418,6 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
 		retval = bpf_flow_dissect(prog, &ctx, eth->h_proto, ETH_HLEN,
 					  size);
 
-		flow_keys.nhoff -= ETH_HLEN;
-		flow_keys.thoff -= ETH_HLEN;
-
 		if (signal_pending(current)) {
 			preempt_enable();
 			rcu_read_unlock();