[PATCH] x86_64: trivial gart clean-up

A trivial change to have gart_unmap_sg call gart_unmap_single directly,
instead of bouncing through the dma_unmap_single wrapper in
dma-mapping.h.

This change required moving the gart_unmap_single above gart_unmap_sg,
and under gart_map_single (which seems a more logical place that its
current location IMHO).

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>