net: ethernet: Add EAPoL ether type support

Wi-Fi protocol uses EAPoL ether type frames for authentication, so, add
support for that ether type so that they are not dropped.

Though we have NET_ETHERNET_FORWARD_UNRECOGNISED_ETHERTYPE to allow
unknown frames to be passed up the stack, but this might cause
performance penalty.

Signed-off-by: Krishna T <krishna.t@nordicsemi.no>