watchdog: orion_wdt: remove orion_wdt_set_timeout

The watchdog core will do the same thing if no set_timeout
is supplied so we can safely remove orion_wdt_set_timeout.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
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>