selftests/bpf: remove wrong nhoff in flow dissector test

.nhoff = 0 is (correctly) reset to ETH_HLEN on the next line so let's
drop it.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/prog_tests/flow_dissector.c

@@ -344,7 +344,6 @@ struct test tests[] = {
 			.tcp.dest = 8080,
 		},
 		.keys = {
-			.nhoff = 0,
 			.nhoff = ETH_HLEN,
 			.thoff = ETH_HLEN + sizeof(struct iphdr) +
 				sizeof(struct iphdr),