watchdog: orion: fix platform_get_irq() complaints

Fix:

orion_wdt f1020300.watchdog: IRQ index 1 not found

which is caused by platform_get_irq() now complaining when optional
IRQs are not found.  Neither interrupt for orion is required, so
make them both optional.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/E1iahcN-0000AT-Co@rmk-PC.armlinux.org.uk
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>