This is minor "obvious" fixes plus two tweaks to help later
patches:

    - Interrupt QH has a link to the device, needed to implement
      schedule trees (like OHCI does today) that are TT-aware
      (essential for most keyboards and mice).

    - Export the macros that do high bandwidth packetsize stuff.
      They're also needed for high bandwidth ISO transfers.

It also morphs some existing "too much debug info" urb tracing
so it's kicked in by a manual #define EHCI_URB_TRACE.  If some
generic version of that gets added to usbcore, this sort
of debug code can vanish (from all hcds).