drivers: misc: add Gateworks System Controller driver

Add a driver for the Gateworks System Controller used on Gateworks boards
which provides a boot watchdog, power control, temperature monitor,
and voltage ADCs.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>

include/gsc.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2022 Gateworks Corporation
+ */
+
+#ifndef _GSC_H_
+#define _GSC_H_
+
+/*
+ * board_gsc_info - Display additional board info
+ */
+void board_gsc_info(void);
+
+/*
+ * gsc_boot_wd_disable - disable the BOOT watchdog
+ *
+ * Return: 0 on success or negative error on failure
+ */
+int gsc_boot_wd_disable(void);
+
+#endif