selftests/bpf: Enable config options needed for xdp_synproxy test

This commit adds the kernel config options needed to run the recently
added xdp_synproxy test. Users without these options will hit errors
like this:

test_synproxy:FAIL:iptables -t raw -I PREROUTING         -i tmp1 -p
tcp -m tcp --syn --dport 8080 -j CT --notrack unexpected error: 256
(errno 22)

Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220620104939.4094104-1-maximmi@nvidia.com