iommu/vt-d: Differentiate relaxable and non relaxable RMRRs

Now we have a new IOMMU_RESV_DIRECT_RELAXABLE reserved memory
region type, let's report USB and GFX RMRRs as relaxable ones.

We introduce a new device_rmrr_is_relaxable() helper to check
whether the rmrr belongs to the relaxable category.

This allows to have a finer reporting at IOMMU API level of
reserved memory regions. This will be exploitable by VFIO to
define the usable IOVA range and detect potential conflicts
between the guest physical address space and host reserved
regions.

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>