KVM: arm/arm64: vgic-new: Wire up irqfd injection

Connect to the new VGIC to the irqfd framework, so that we can
inject IRQs.
GSI routing and MSI routing is not yet implemented.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>