x86, AMD IOMMU: include amd_iommu_last_bdf in device initialization

All the values read while searching for amd_iommu_last_bdf are defined as
inclusive. Let the code handle this value as such. Found by Wei Wang. Thanks
Wei.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: iommu@lists.linux-foundation.org
Cc: bhavna.sarathy@amd.com
Cc: robert.richter@amd.com
Cc: Wei Wang <wei.wang2@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>