[NETFILTER]: nfnetlink_queue: remove useless enqueue status codes

The queueing core doesn't care about the exact return value from
the queue handler, so there's no need to go through the trouble
of returning a meaningful value as long as we indicate an error.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>