Update copyright line to 2015
diff --git a/library/pbkdf2.c b/library/pbkdf2.c
index 66e8c21..479ed0f 100644
--- a/library/pbkdf2.c
+++ b/library/pbkdf2.c
@@ -6,7 +6,7 @@
  *
  * \author Mathias Olsson <mathias@kompetensum.com>
  *
- *  Copyright (C) 2006-2012, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *
  *  This file is part of mbed TLS (https://polarssl.org)
  *