(Supplements: ee999d8b)

NFPROTO_ARP actually has a different value from NF_ARP, so ensure all
callers use the new value so that packets _do_ get delivered to the
registered hooks.
Signed-off-by: NJan Engelhardt <jengelh@medozas.de>
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>