netx: Move the netx driver

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

CC: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>