esp_system: Make interrupt WDT private API

This commit makes the interrupt WDT API private. To use the API,
IDF components should now '#include "esp_private/esp_int_wdt.h"'

components/esp_system/include/esp_private/esp_int_wdt.h

@@ -0,0 +1,59 @@
+/*
+ * SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef __ESP_INT_WDT_H
+#define __ESP_INT_WDT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** @addtogroup Watchdog_APIs
+  * @{
+  */
+
+/*
+This routine enables a watchdog to catch instances of processes disabling
+interrupts for too long, or code within interrupt handlers taking too long.
+It does this by setting up a watchdog which gets fed from the FreeRTOS
+task switch interrupt. When this watchdog times out, initially it will call
+a high-level interrupt routine that will panic FreeRTOS in order to allow
+for forensic examination of the state of the both CPUs. When this interrupt
+handler is not called and the watchdog times out a second time, it will
+reset the SoC.
+
+This uses the TIMERG1 WDT.
+*/
+
+
+/**
+  * @brief  Initialize the non-CPU-specific parts of interrupt watchdog.
+  *         This is called in the init code if the interrupt watchdog
+  *         is enabled in menuconfig.
+  *
+  */
+void esp_int_wdt_init(void);
+
+/**
+  * @brief  Enable the interrupt watchdog on the current CPU. This is called
+  *         in the init code by both CPUs if the interrupt watchdog is enabled
+  *         in menuconfig.
+  *
+  */
+void esp_int_wdt_cpu_init(void);
+
+
+
+/**
+  * @}
+  */
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif