cmd/internal/obj: add copyright header to files

Change-Id: I4ed33f3fdb9ad5f0f8984d3ef282c34e26eb2cde
Reviewed-on: https://go-review.googlesource.com/21301Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/internal/obj/arm64/anames7.go

+// Copyright 2015 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.
+
 package arm64
 
 var cnames7 = []string{

src/cmd/internal/obj/mips/anames0.go

+// Copyright 2015 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.
+
 package mips
 
 var cnames0 = []string{

src/cmd/internal/obj/ppc64/anames9.go

+// Copyright 2015 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.
+
 package ppc64
 
 var cnames9 = []string{