watchdog: da9062: remove unused code

The patch "watchdog: da9062: use protection delay mechanism from core"
(fb484262) removed the only user of j_time_stamp. This turned into some
leftover functions that are removed with this patch.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>