Standardize Levitte's dual-license

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3689)

crypto/LPdir_unix.c

diff --git a/crypto/LPdir_unix.c b/crypto/LPdir_unix.c
index 1bb2940..1599a6f 100644
--- a/crypto/LPdir_unix.c
+++ b/crypto/LPdir_unix.c
@@ -8,6 +8,9 @@
  */
 
 /*
+ * This file is dual-licensed and is also avialable under the following
+ * terms:
+ *
  * Copyright (c) 2004, Richard Levitte <richard@levitte.org>
  * All rights reserved.
  *