drivers: clk: Update license for Intel N5X device

All the source code of clk-mem-n5x.c and clk-n5x.c are from Intel,
update the license to use both GPL2.0 and BSD-3 Clause because this
copy of code may used for open source and internal project.

Signed-off-by: Teik Heng Chong <teik.heng.chong@intel.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@intel.com>
diff --git a/drivers/clk/altera/clk-mem-n5x.c b/drivers/clk/altera/clk-mem-n5x.c
index ca44998..9bbe2cd 100644
--- a/drivers/clk/altera/clk-mem-n5x.c
+++ b/drivers/clk/altera/clk-mem-n5x.c
@@ -1,6 +1,6 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 /*
- * Copyright (C) 2020-2021 Intel Corporation <www.intel.com>
+ * Copyright (C) 2020-2022 Intel Corporation <www.intel.com>
  */
 
 #include <common.h>