internal/socket: add support for openbsd/arm64
internal/socket: add support for openbsd/arm64

Updates golang/go#31656

Change-Id: I238655c111e8422c60d20d853aeb965be16c1c7e
Reviewed-on: https://go-review.googlesource.com/c/net/+/181617
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/net