windows: remove unused asm.s

Change-Id: I1a2b96f71c9f39a46827e9414e1058894fd2a5e1
Reviewed-on: https://go-review.googlesource.com/21523Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

windows/asm.s

-// Copyright 2014 The Go Authors.  All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build windows
-
-#include "textflag.h"
-
-TEXT ·use(SB),NOSPLIT,$0
-	RET

windows/syscall.go

@@ -23,7 +23,6 @@ package windows // import "golang.org/x/sys/windows"
 
 import (
 	"syscall"
-	"unsafe"
 )
 
 // ByteSliceFromString returns a NUL-terminated slice of bytes
@@ -70,8 +69,3 @@ func (ts *Timespec) Nano() int64 {
 func (tv *Timeval) Nano() int64 {
 	return int64(tv.Sec)*1e9 + int64(tv.Usec)*1000
 }
-
-// use is a no-op, but the compiler cannot see that it is.
-// Calling use(p) ensures that p is kept live until that point.
-//go:noescape
-func use(p unsafe.Pointer)