Packets defragmentation was introduced for PACKET_FANOUT_HASH only,
see 7736d33f ("packet: Add pre-defragmentation support for ipv4
fanouts")

It may be useful to have defragmentation enabled regardless of
fanout type. Without that, the AF_PACKET user may have to:
1. Collect fragments from different rings
2. Defragment by itself
Signed-off-by: Alexander Drozdov <al.drozdov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>