internal/socket: add support for openbsd/mips64
internal/socket: add support for openbsd/mips64

For golang/go#40995

Change-Id: I415ce04a3fb419de933ab4bb5d2afbacbbaff80c
Reviewed-on: https://go-review.googlesource.com/c/net/+/274772
Trust: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Joel Sing <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@sing.id.au>

golang/net