AMD,IOMMU: Disable IOMMU if SATA Combined mode is on

AMD,IOMMU: Disable IOMMU if SATA Combined mode is on

AMD's SP5100 chipset can be placed into SATA Combined mode
that may cause prevent dom0 from booting when IOMMU is
enabled and per-device interrupt remapping table is used.
While SP5100 erratum 28 requires BIOSes to disable this mode,
some may still use it.

This patch checks whether this mode is on and, if per-device
table is in use, disables IOMMU.

This is XSA-36 / CVE-2013-0153.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@amd.com>
Flipped operands of && in amd_iommu_init() to make the message issued
by amd_sp5100_erratum28() match reality (when amd_iommu_perdev_intremap
is zero, there's really no point in calling the function).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Committed-by: Jan Beulich <jbeulich@suse.com>