iommu/vt-d: Enable PCI/IMS

PCI/IMS works like PCI/MSI-X in the remapping. Just add the feature flag,
but only when on real hardware.

Virtualized IOMMUs need additional support, e.g. for PASID.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221124232327.081482253@linutronix.de