xircom: Move the Xircom driver

Move the Xircom driver into drivers/net/ethernet/xircom/ and
make the necessary Kconfig and Makefile changes.

CC: <psheer@icon.co.za>
CC: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>