[PKTGEN]: Remove write-only variable.

The pktgen_thread.pid is set to current->pid and is never used
after this. So remove this at all.

Found during isolating the explicit pid/tgid usage.

Signed-off-by: Pavel Emelyanov <[e-mail]>
Acked-by: Sukadev Bhattiprolu <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/pktgen.c

···
 	/* Field for thread to receive "posted" events terminate, stop ifs etc. */
 
 	u32 control;
-	int pid;
 	int cpu;
 
 	wait_queue_head_t queue;
···
 	BUG_ON(smp_processor_id() != cpu);
 
 	init_waitqueue_head(&t->queue);
-
-	t->pid = current->pid;
 
 	pr_debug("pktgen: starting pktgen/%d:  pid=%d\n", cpu, current->pid);