arm64: dts: fast models: Fix FVP PCI interrupt-map property

The interrupt map for the FVP's PCI node is missing the
parent-unit-address cells for each of the INTx entries, leading to the
kernel code failing to parse the entries correctly.

Add the missing zero cells, which are pretty useless as far as the GIC
is concerned, but that the spec requires. This allows INTx to be usable
on the model, and VFIO to work correctly.

Fixes: fa083b99

 ("arm64: dts: fast models: Add DTS fo Base RevC FVP")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>