udev: net_id - for ccw bus, shorten the identifier and stip leading zeros

udev: net_id - for ccw bus, shorten the identifier and stip leading zeros

The commmon case default qeth link is enccw0.0.0600 is rather long.

Thus strip leading zeros (which doesn't make the bus_id unstable),
similar to the PCI domain case.

Also 'ccw' is redundant on S/390, as there aren't really other buses
available which could have qeth driver interfaces. Not sure why this
code is even compiled on non-s390[x] platforms. But to distinguish from
e.g. MAC stable names shorten the suffix to just 'c'.

Thus enccw0.0.0600 becomes enc600.