Attached is a patch leveraging some of the new generic dma stuff:

- Replaces dma mapping calls in usbcore with generic equivalents.
   This is a minor code shrink (which we'd hoped could happen).

- Pass dma mask along, so net drivers can notice it'd be good to
   set NETIF_F_HIGHDMA; or scsi ones can set highmem_io.  (Some
   Intel EHCI setups are able to support this kind of DMA.)

- Updates one net driver (usbnet) to set NETIF_F_HIGHDMA when
   appropriate, mostly as an example (since I can't test this).

- Provides Documentation/usb/dma.txt, describing current APIs.
   (Unchanged by this patch, except dma mask visibility.)

- Converted another info() to dev_info(), and likewise a couple
   dbg() to dev_dbg() conversions in the modified routine.

The number of FIXMEs was conserved: the generic API doesn't yet
fix the error reporting bugs in the PCI-specific mapping API.