hw/arm/virt: Set PCI preserve_config for accel SMMUv3

hw/arm/virt: Set PCI preserve_config for accel SMMUv3

Introduce a new pci_preserve_config field in virt machine state which
allows the generation of DSM #5. This field is only set if accel SMMU
is instantiated.

In a subsequent patch, SMMUv3 accel mode will make use of IORT RMR nodes
to enable nested translation of MSI doorbell addresses. IORT RMR requires
_DSM #5 to be set for the PCI host bridge so that the Guest kernel
preserves the PCI boot configuration.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
Message-id: 20260126104342.253965-24-skolothumtho@nvidia.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>