This updates the Philips tweak so that it also applies
to late-model ICH chips from Intel.  (Or so I'm told ... :)
That's at least three EHCI implementations known to
behave on Linux.  (And one hopes VIA soon too...)

It also cleans up a few comments relating to 64bit DMA;
recent API spec updates make it look like no games are
needed with the PCI DMA mask -- it doesn't change the
segment used by pci_pool allocations, so it just needs
to get turned on if the overall system does 64bit DMA.

I've a query in to see if those Philips/Intel tweaks are
chip quirks, or just something the EHCI 1.0 spec isn't
at all clear about.