This patch changes how usbnet and CDC Ether get configured,
switching to the newer implementation with that CDC model
(using a "minidriver" for "usbnet").

  - Removes "cdc-ether" from Kconfig and Makefile.
    Once everything flies, "cdc-ether.c" can be
    removed from the kernel.

  - Makes all the "minidriver" options in "usbnet"
    explicit in Kconfig, defaulting to "y" for most
    cases.  So folk expecting a CDC Ether option in
    Kconfig will still have one, and during config
    a list of hardware (cables, PDAs, etc) using the
    "usbnet" driver is now available.  (It's possible
    to save a few pages of code by configuring out
    drivers that use custom framing.)

  - Since now it's possible to create broken configs,
    this checks for them.  The two basic errors being
    configuring "usbnet" with no minidrivers, and
    needing to blacklist Zaurus in CDC-only configs.

  - Zaurus shouldn't do full CDC style init, since it
    doesn't uniquify the Ethernet address it reports;
    and it still shouldn't come up as an "eth%d" link.

The CDC support is still "experimental", since I want
to see a few interop reports for commercial products
before changing that.