e1000e: add device IDs for i218

i218 is the next-generation LOM that will be available on systems with the
Lynx Point LP Platform Controller Hub (PCH) chipset from Intel.  This patch
provides the initial support of those devices.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>