x86: move pci fixup to pci-dma.c

via_no_dac provides a fixup that is the same for both
architectures. Move it to pci-dma.c.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>