selftests/bpf: Use make_sockaddr in test_sock_addr

This patch uses public helper make_sockaddr() exported in network_helpers.h
instead of the local defined function mk_sockaddr() in test_sock_addr.c.
This can avoid duplicate code.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/1473e189d6ca1a3925de4c5354d191a14eca0f3f.1713868264.git.tanggeliang@kylinos.cn


Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>