iommu/vt-d: Unify the way to process DMAR device scope array

Now we have a PCI bus notification based mechanism to update DMAR
device scope array, we could extend the mechanism to support boot
time initialization too, which will help to unify and simplify
the implementation.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>