net: Delete isa-skeleton net driver

The ISA skeleton net driver has been obsolete and unmaintained for many
years.  Any hardware remotely like ISA will use the platform API and
look much more like a PCI driver, and make much better use of netdev
APIs such as NAPI.
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>