selftest: tcp: Make bind() selftest flexible.

Currently, bind_wildcard.c tests only (IPv4, IPv6) pairs, but we will
add more tests for the same protocol pairs.

This patch makes it possible by changing the address pointer to void.

No functional changes are intended.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240326204251.51301-4-kuniyu@amazon.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>