options/bsd: move getifaddrs from linux to bsd

[marv7000]

getifaddrs is also available on different BSDs. The function signatures and struct ifaddrs aligns with the current mlibc declaration.

[no92]

Given that it is also supported on Linux, I am not sure that moving it is the best play - maybe we should enable it if __MLIBC_LINUX_OPTION || __MLIBC_BSD_OPTION?

[mintsuki]

Agreed.