The barebox watchdog poller uses the struct watchdog.timeout_cur as
the timeout value to configure the watchdog with.

There's no need for the device driver to set this. I didn't know that
when I wrote the drivers, but I do now, hence this commit.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>