This patch fixes two problems that have already been discussed
on this list:

- USB_QUEUE_BULK is rather pointless (and UHCI-specific).
   If drivers really want only one bulk urb queued at a time,
   they just shouldn't issue such urbs till others complete.

     FIX:  remove it entirely.

- USB_DISABLE_SPD is horribly named (based on a UHCI flag).
   What it really does is turn non-ISO short reads into errors.

     FIX:  rename it.  Now it's URB_SHORT_NOT_OK.

I changed all the drivers using these two flags, including
corresponding changes in the "usbfs" API.

Most of the patch by volume is doc updates:

- Documentation/usb/URB.txt hadn't been updated in two years (!)
   and was pretty out of date.  It also had many details that were
   inappropriately specific to usb-uhci.
- Most of the URB flags weren't even commented as to intent.
- DISABLE_SPD was often documented as if it were SHORT_IS_OK.
- There was still some doc saying how iso should use urb->next.

There are also some related updates:

- Some of the submit sanity checks for transfer flags were
   overly broad ... SHORT_NOT_OK is only for reads, NO_FSBR
   is for non-periodic requests, ZERO_PACKET only for writes.
- The ohci-hcd code thought SHORT_NOT_OK worked for ISO.
- The uhci-hcd code thought QUEUE_BULK applied to non-bulk

Note that this patch doesn't update any of the "old" HCDs,
including usb-ohci-hcd.

In the case of usb-uhci{,-hcd} it'd have been painful to fix
the QUEUE_BULK logic.  That logic was, I think, the original
reason to have that flag!  So I count switching to "uhci-hcd"
as a win already ... :)