Revert "ipv4, ipv6, internal/netreflect, bpf: fix the x/net build"

This reverts https://go-review.googlesource.com/c/37401

Updates golang/go#19051.

Change-Id: Ia3cbc42213e3c519f91650e6308a7ca1f56b6189
Reviewed-on: https://go-review.googlesource.com/37417
Reviewed-by: Ian Lance Taylor <iant@golang.org>
6 files changed