Update copyright notices to use Linux Foundation guidance

As a result, the copyright of contributors other than Arm is now
acknowledged, and the years of publishing are no longer tracked in the
source files.

Also remove the now-redundant lines declaring that the files are part of
MbedTLS.

This commit was generated using the following script:

# ========================
#!/bin/sh

# Find files
find '(' -path './.git' -o -path './3rdparty' ')' -prune -o -type f -print | xargs sed -bi '

# Replace copyright attribution line
s/Copyright.*Arm.*/Copyright The Mbed TLS Contributors/I

# Remove redundant declaration and the preceding line
$!N
/This file is part of Mbed TLS/Id
P
D
'
# ========================

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
diff --git a/tests/scripts/generate_code.pl b/tests/scripts/generate_code.pl
index 2c20399..bca7cac 100755
--- a/tests/scripts/generate_code.pl
+++ b/tests/scripts/generate_code.pl
@@ -2,7 +2,7 @@
 
 # generate_code.pl
 #
-# Copyright (c) 2009-2016, ARM Limited, All Rights Reserved
+# Copyright The Mbed TLS Contributors
 # SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 #
 # This file is provided under the Apache License 2.0, or the
@@ -44,8 +44,6 @@
 #
 # **********
 #
-# This file is part of Mbed TLS (https://tls.mbed.org)
-#
 # Purpose
 #
 # Generates the test suite code given inputs of the test suite directory that
@@ -222,8 +220,6 @@
  *      Test suite file : $test_case_file
  *      Test suite data : $test_case_data
  *
- *
- *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 
 #if !defined(MBEDTLS_CONFIG_FILE)