watchdog: intel-mid_wdt: Convert to use new SCU IPC API

This converts the Intel MID watchdog driver over the new SCU IPC API
where the SCU IPC instance is passed to the functions.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>