watchdog: da9063: remove duplicated timeout_to_sel calls

Every time da9063_wdt_update_timeout() gets called a timeout_to_sel() is
made because the timeout argument of update_timeout() is the raw
register value. Moving the second<->raw-value translation into
da9063_wdt_update_timeout() removes duplicated code.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Acked-by: Steve Twiss <stwiss.opensource@diasemi.com>
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>