irqchip: versatile-fpga: add new compatible for OX810SE SoC

Under the OX810SE, this exact same interface is used as "Reference Peripheral
Specification" Interrupt Controller, so add a new compatible string in order
to support the Oxford Semiconductor OX810SE SoC interrupt controller.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>