amd-iommu: fix iommu flag masks

The feature bits should be set via bitmasks, not via feature IDs.

[ Impact: fix feature enabling in newer IOMMU versions ]

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
LKML-Reference: <20090504102028.GA30307@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>