[NETPOLL]: rx_flags bugfix

Initialize npinfo->rx_flags.  The way it stands now, this will have random
garbage, and so will incur a locking penalty even when an rx_hook isn't
registered and we are not active in the netpoll polling code.
Signed-off-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NMatt Mackall <mpm@selenic.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/netpoll.c

@@ -639,6 +639,7 @@ int netpoll_setup(struct netpoll *np)
 		if (!npinfo)
 			goto release;
 
+		npinfo->rx_flags = 0;
 		npinfo->rx_np = NULL;
 		npinfo->poll_lock = SPIN_LOCK_UNLOCKED;
 		npinfo->poll_owner = -1;