p256-x86_64-asm.pl: Add OpenSSL copyright

As of upstream's 6aa36e8e5a062e31543e7796f0351ff9628832ce, the
corresponding file in OpenSSL has both an Intel and OpenSSL copyright
blocks.  To properly sync up with OpenSSL, use the OpenSSL copyright
block and our version of the Intel copyright block.

Change-Id: I4dc072a11390a54d0ce38ec0b8893e48f52638de
Reviewed-on: https://boringssl-review.googlesource.com/25585
Reviewed-by: Adam Langley <agl@google.com>

crypto/fipsmodule/ec/asm/p256-x86_64-asm.pl

@@ -1,4 +1,10 @@
-#!/usr/bin/env perl
+#! /usr/bin/env perl
+# Copyright 2014-2016 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the OpenSSL license (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
 
 # Copyright (c) 2014, Intel Corporation.
 #