AMD/IOMMU: convert amd_iommu_pte from struct to union

AMD/IOMMU: convert amd_iommu_pte from struct to union

This is to add a "raw" counterpart to the bitfield equivalent. Take the
opportunity and
 - convert fields to bool / unsigned int,
 - drop the naming of the reserved field,
 - shorten the names of the ignored ones.

This is part of XSA-347.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Paul Durrant <paul@xen.org>
master commit: 73f62c7380edf07469581a3049aba98abd63b275
master date: 2020-10-20 14:22:26 +0200