net: fix can_checksum_protocol() arguments swap

commit 03634668 (net offloading: Convert checksums to use
centrally computed features.) mistakenly swapped can_checksum_protocol()
arguments.

This broke IPv6 on bnx2 for instance, on NIC without TCPv6 checksum
offloads.

Reported-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>