revert commit 58a09b38
("[libata] ahci: Restore SB600 SATA controller 64 bit DMA")

Upstream commit 58a09b38 does
nearly the same thing but this patch is simplified for 2.6.31

Disables 64-bit DMA for _all_ boards, unlike 2.6.32 which adds a
whitelist. (The whitelist function requires a fairly large patch
that touches unrelated code.)

Doesn't revert the DMI part as other backported patches might need
the exported symbol.

Applies to 2.6.31.4
Signed-off-by: Chuck Ebbert <cebbert@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>