internal/socket: delete darwin/{386,arm} code

This repo supports the latest two Go releases (currently Go 1.17 and
1.18) and tip.

The darwin/386 and darwin/arm ports were already dropped in Go 1.15.
Delete them from this package as well.

Change-Id: Iec878ae83930a585649726e1363bc53d98b3afee
Reviewed-on: https://go-review.googlesource.com/c/net/+/419936
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

internal/socket/zsys_darwin_386.go

@@ -1,30 +0,0 @@
-// Code generated by cmd/cgo -godefs; DO NOT EDIT.
-// cgo -godefs defs_darwin.go
-
-package socket
-
-type iovec struct {
-	Base *byte
-	Len  uint32
-}
-
-type msghdr struct {
-	Name       *byte
-	Namelen    uint32
-	Iov        *iovec
-	Iovlen     int32
-	Control    *byte
-	Controllen uint32
-	Flags      int32
-}
-
-type cmsghdr struct {
-	Len   uint32
-	Level int32
-	Type  int32
-}
-
-const (
-	sizeofIovec  = 0x8
-	sizeofMsghdr = 0x1c
-)

internal/socket/zsys_darwin_arm.go

@@ -1,30 +0,0 @@
-// Code generated by cmd/cgo -godefs; DO NOT EDIT.
-// cgo -godefs defs_darwin.go
-
-package socket
-
-type iovec struct {
-	Base *byte
-	Len  uint32
-}
-
-type msghdr struct {
-	Name       *byte
-	Namelen    uint32
-	Iov        *iovec
-	Iovlen     int32
-	Control    *byte
-	Controllen uint32
-	Flags      int32
-}
-
-type cmsghdr struct {
-	Len   uint32
-	Level int32
-	Type  int32
-}
-
-const (
-	sizeofIovec  = 0x8
-	sizeofMsghdr = 0x1c
-)