lantiq: Move the Lantiq SoC driver

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

CC: John Crispin <blogic@openwrt.org>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: John Crispin <blogic@openwrt.org>