drivers/wdt: Rename STM32 IWDG files to follow naming rules

Basically, all driver file names should start with the driver type as
prefix: wdt_ in case of watchdogs here.

Maybe 'iwdg' keyword could be removed entirely, and also in function
names. However that is not the scope of this patch.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>

drivers/watchdog/CMakeLists.txt

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 zephyr_sources_ifdef(CONFIG_WDT_QMSI wdt_qmsi.c)
-zephyr_sources_ifdef(CONFIG_IWDG_STM32 iwdg_stm32.c)
+zephyr_sources_ifdef(CONFIG_IWDG_STM32 wdt_iwdg_stm32.c)
 zephyr_sources_ifdef(CONFIG_WDOG_CMSDK_APB wdog_cmsdk_apb.c)
 zephyr_sources_ifdef(CONFIG_WDT_SAM wdt_sam.c)
 zephyr_sources_ifdef(CONFIG_WDT_ESP32 wdt_esp32.c)

drivers/watchdog/wdt_iwdg_stm32.c

@@ -11,7 +11,7 @@
 #include <errno.h>
 #include <assert.h>
 
-#include "iwdg_stm32.h"
+#include "wdt_iwdg_stm32.h"
 
 /* Minimal timeout in microseconds. */
 #define IWDG_TIMEOUT_MIN	100