This allows userspace to use bulk-streams, just like in kernel drivers, see
Documentation/usb/bulk-streams.txt for details on the in kernel API. This
is exported pretty much one on one to userspace.

To use streams an app must first make a USBDEVFS_ALLOC_STREAMS ioctl,
on success this will return the number of streams available (which may be
less then requested). If there are n streams the app can then submit
usbdevfs_urb-s with their stream_id member set to 1-n to use a specific
stream. IE if USBDEVFS_ALLOC_STREAMS returns 4 then stream_id 1-4 can be
used.

When the app is done using streams it should call USBDEVFS_FREE_STREAMS

Note applications are advised to use libusb rather then using the
usbdevfs api directly. The latest version of libusb has support for streams.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>