hw/arm/virt: Use "msi-map" devicetree property for PCI

The "msi-parent" property can be used on the PCI node when MSIs do not
contain sideband data (device IDs) [1]. In QEMU, MSI transactions
contain the requester ID, so the PCI node should use the "msi-map"
property instead of "msi-parent". In our case the property describes an
identity map between requester ID and sideband data.

This fixes a warning when passing the DTB generated by QEMU to dtc,
following a recent change to the GICv3 node:

  Warning (msi_parent_property): /pcie@10000000:msi-parent: property size (4) too small for cell size 1

[1] linux/Documentation/devicetree/bindings/pci/pci-msi.txt

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20220927100347.176606-4-jean-philippe@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>