Some models use Intel I219-V instead of the Realtek RTL8111 controller.
Introduce a new variant so the IFD of the Realtek board does not have
the onboard LAN enabled when it is not connected.
Change-Id: I1961a7a8fac2dc6e81ebae013ff62cd491fba43c
Signed-off-by: Tim Crawford <tcrawford@system76.com>