virtio-iommu : Retrieve page size mask on virtio_iommu_set_iommu_device()

virtio-iommu : Retrieve page size mask on virtio_iommu_set_iommu_device()

Retrieve the Host IOMMU Device page size mask when this latter is set.
This allows to get the information much sooner than when relying on
IOMMU MR set_page_size_mask() call, whcih happens when the IOMMU MR
gets enabled. We introduce check_page_size_mask() helper whose code
is inherited from current virtio_iommu_set_page_size_mask()
implementation. This callback will be removed in a subsequent patch.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>