The dma hooks whereby EHCI can pass 64bit DMA support
up the driver stack (to avoid buffer copies) turn out
to broken on most architectures(*).  This patch just
disables them all, since it looks like those mechanisms
won't get fixed before 2.6.0-final.  For now it'd only
matter on a few big Intel boxes anyway.

Please merge.

- Dave

(*) On x86, mips, and arm dma_supported() doesn't
     even compare with the device's mask.  On several
     other architectures (reported on ppc, alpha,
     and sparc64), asking that question for non-PCI
     devices will just BUG() -- even though all info
     needed to answer the question is right at hand.