atl2: add atl2 driver

Driver for Atheros L2 10/100 network device. Includes necessary
changes for Kconfig, Makefile, and pci_ids.h.

Signed-off-by: Chris Snook <csnook@redhat.com>
Signed-off-by: Jay Cliburn <jacliburn@bellsouth.net>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>