watchdog: ftwdt010_wdt: implement _restart() function

watchdog: ftwdt010_wdt: implement _restart() function

Implement ftwdt010_wdt_restart(). It enables watchdog with timeout = 0
and disabled IRQ. Since it needs code similar to ftwdt010_wdt_start(),
add a new function ftwdt010_enable() and move common code there.

Suggested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sergei Antonov <saproj@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220829090436.452742-1-saproj@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>