watchdog: stm32: Fix copyright

Uniformize STMicroelectronics copyrights header
Add SPDX identifier

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Acked-by: Alexandre TORGUE <alexandre.torgue@st.com>
CC: Yannick Fertre <yannick.fertre@st.com>
Acked-by: Yannick Fertre <yannick.fertre@st.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/stm32_iwdg.c

@@ -1,12 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Driver for STM32 Independent Watchdog
  *
- * Copyright (C) Yannick Fertre 2017
- * Author: Yannick Fertre <yannick.fertre@st.com>
+ * Copyright (C) STMicroelectronics 2017
+ * Author: Yannick Fertre <yannick.fertre@st.com> for STMicroelectronics.
  *
  * This driver is based on tegra_wdt.c
  *
- * License terms:  GNU General Public License (GPL), version 2
  */
 
 #include <linux/clk.h>