iommu/vt-d: Make first level IOVA canonical

First-level translation restricts the input-address to a canonical
address (i.e., address bits 63:N have the same value as address
bit [N-1], where N is 48-bits with 4-level paging and 57-bits with
5-level paging). (section 3.6 in the spec)

This makes first level IOVA canonical by using IOVA with bit [N-1]
always cleared.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>