It doesn't depend on either usb-net or usb-net-cdc-ncm. It does, however, depend
on mii. Fix thusly, and make it depend explicitly on usb, not usb-net.
While at it, add a conditional dependency on libphy, for future kernel versions.
Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
371cad4f28