x86, AMD IOMMU: disable suspend/resume with IOMMU enabled (for now)

This patch disables suspend/resume on machines with AMD IOMMU enabled. Real
suspend/resume support for AMD IOMMU is currently being worked on. Until this
is ready it will be disabled to avoid data corruption when the IOMMU is not
properly re-enabled at resume. The patch is based on a similar patch for the
GART driver written by Pavel Machek.

The overall driver merged into tip/master is tested with parallel disk and
network loads and showed no problems in a test running for 3 days.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: iommu@lists.linux-foundation.org
Cc: bhavna.sarathy@amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>