remove spurious TODO

we create the AF_PACKET socket with protocol=0 ie. 'ETH_P_NONE'

as such initially the socket cannot receive any packets,
but can be used for transmit.

then we bind it to ETH_P_ARP + ifindex, as such we will only
ever receive ARP packets on that interface.

Test: comment only change
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I9075086d9582b8a8879cd5c7e4f46b78c9e2fede