Impact: cleanup, remove dead code

The last usage was removed by the patch set culminating in

| commit e3c449f5
| Author: Joerg Roedel <joerg.roedel@amd.com>
| Date:   Wed Oct 15 22:02:11 2008 -0700
|
|     x86, AMD IOMMU: convert driver to generic iommu_num_pages function
Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>