Verify that MAC address checks are needed

[cjdoucette]

The LLS block currently checks to make sure that we're only receiving packets that are destined to us, which is one of four L2 addresses. The NIC should be able to handle this functionality, so we should verify that it can (and that all NICs in our deployment do the same).

This feature should remove the relevant XXX in lls/main.c.

[AltraMayor]

Doesn't lls/main.c:process_pkts() only receive IPv4 packets? If so, even if the test on eth_hdr->d_addr should be kept, the test doesn't need to include iface->eth_mc_addr and iface->ll_eth_mc_addr since this Ethernet addresses are meant to support IPv6, not IPv4.