acenic: Move the Alteon driver

Based on feedback from Alan Cox, the acenic driver moved to
drivers/net/ethernet/alteon/ and made the necessary Kconfig and
Makefile changes.

CC: Jes Sorensen <jes@trained-monkey.org>
CC: Alan Cox <alan@linux.intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>