iommu/vt-d: Handle PCI bridge RMRR device scopes in intel_iommu_get_resv_regions

In the case the RMRR device scope is a PCI-PCI bridge, let's check
the device belongs to the PCI sub-hierarchy.

Fixes: 0659b8dc

 ("iommu/vt-d: Implement reserved region get/put callbacks")

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>