pktgen: Fix freezing problem

Add missing try_to_freeze() to one of the pktgen_thread_worker() code
paths so that it doesn't block suspend/hibernation.

Fixes http://bugzilla.kernel.org/show_bug.cgi?id=15006

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Reported-and-tested-by: Ciprian Dorin Craciun <ciprian.craciun@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/pktgen.c

@@ -3524,6 +3524,7 @@ static int pktgen_thread_worker(void *arg)
 			wait_event_interruptible_timeout(t->queue,
 							 t->control != 0,
 							 HZ/10);
+			try_to_freeze();
 			continue;
 		}