x86/PCI: build failure at x86/kernel/pci-dma.c with !CONFIG_PCI

On Thu, Oct 23, 2008 at 04:09:52PM -0700, Alexander Beregalov wrote:
> arch/x86/kernel/built-in.o: In function `iommu_setup':
> pci-dma.c:(.init.text+0x36ad): undefined reference to `forbid_dac'
> pci-dma.c:(.init.text+0x36cc): undefined reference to `forbid_dac'
> pci-dma.c:(.init.text+0x3711): undefined reference to `forbid_dac

This patch partially reverts a patch to add IOMMU support to ia64.  The
forbid_dac variable was incorrectly moved to quirks.c, which isn't built
when PCI is disabled.

Tested-by: "Alexander Beregalov" <a.beregalov@gmail.com>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>