[PATCH] x86_64: pci-dma.c clean-up - trivial

Replace hard coded DMA masks with #defines from
include/linux/dma-mapping.h

Signed-off-by: Jon Mason <jdmason@us.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>