bpf: ARP and BOOTP filter improvements

bpf: ARP and BOOTP filter improvements

The ARP filter now checks hardware and protocol length matches
the interface, it's not from the interface itself and either the
source ip or target ip is one of our addresses of interest.

The BOOTP filter now checks for BOOTREPLY and matching xid.
If the interface hardware address fits inside chaddr then
that is checked as well.