bsd: fix clang warning about alignment problem with sockaddr

bsd: fix clang warning about alignment problem with sockaddr

While this does not seem to be extensively documented, when casting a
`sockaddr *` to something else, like `sockaddr_dl *`, it is believed
that initially, it was a `sockaddr_dl *`, so there is no alignment
problem in this case. We use a macro to cast to `void *` to avoid the
warning.