[PATCH] x86_64: Fix CONFIG_IOMMU_DEBUG

If CONFIG_IOMMU_DEBUG is set force_iommu defaults to 1. In the case
where no HW IOMMU is present in the machine and we end up using nommu,
leaving force_iommu set to 1 causes dma_alloc_coherent to do the wrong
thing. Therefore, if we end up using nommu, make sure force_iommu is
0.

Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>