cdce(4) improvements

Marc Winiger's cdce(4) improvements were committed earlier today. Here's the commit message:

This improves cdce(4) and makes some devices work that previously did not
(like the Sony Ericsson K610 mobile phone).

- Read hardware address from ethernet descriptor makes the Sony Ericsson
K610 work.
- Add support for status notifications (interrupt endpoint).
- Recognize if there is a union descriptori (thus remove CDCE_NO_UNION).
- Handle wrong union descriptors (master/slave values are swapped)
(Ambit NTL 250)

Diff done by Marc Winiger <mw a t msys ch>, tested by many on different
platforms and with various devices:  cable modems, mobile phones, and,
zaurus as USB function.

ok jsg, claudio, kili

Marc says, "that development is in progress and every dmesg output while attaching and using is welcome as a feedback."