modbus: fix Apache-2.0 SPDX License identifier case

While SPDX license identifiers are usually considered to be
case-insensitive, matching the case of the canonical identifier is
recommended by the SPDX specification.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

subsys/modbus/modbus_client.c

@@ -12,7 +12,7 @@
  *
  *      Copyright 2003-2020 Silicon Laboratories Inc. www.silabs.com
  *
- *                   SPDX-License-Identifier: APACHE-2.0
+ *                   SPDX-License-Identifier: Apache-2.0
  *
  * This software is subject to an open source license and is distributed by
  *  Silicon Laboratories Inc. pursuant to the terms of the Apache License,

subsys/modbus/modbus_internal.h

@@ -13,7 +13,7 @@
  *
  *      Copyright 2003-2020 Silicon Laboratories Inc. www.silabs.com
  *
- *                   SPDX-License-Identifier: APACHE-2.0
+ *                   SPDX-License-Identifier: Apache-2.0
  *
  * This software is subject to an open source license and is distributed by
  *  Silicon Laboratories Inc. pursuant to the terms of the Apache License,

subsys/modbus/modbus_serial.c

@@ -13,7 +13,7 @@
  *
  *      Copyright 2003-2020 Silicon Laboratories Inc. www.silabs.com
  *
- *                   SPDX-License-Identifier: APACHE-2.0
+ *                   SPDX-License-Identifier: Apache-2.0
  *
  * This software is subject to an open source license and is distributed by
  *  Silicon Laboratories Inc. pursuant to the terms of the Apache License,

subsys/modbus/modbus_server.c

@@ -12,7 +12,7 @@
  *
  *      Copyright 2003-2020 Silicon Laboratories Inc. www.silabs.com
  *
- *                   SPDX-License-Identifier: APACHE-2.0
+ *                   SPDX-License-Identifier: Apache-2.0
  *
  * This software is subject to an open source license and is distributed by
  *  Silicon Laboratories Inc. pursuant to the terms of the Apache License,