misc: genwqe: fix compile warnings

Using the following command will get compile warnings:
make W=1 drivers/misc/genwqe/card_ddcb.o ARCH=x86_64

drivers/misc/genwqe/card_ddcb.c: In function setup_ddcb_queue:
drivers/misc/genwqe/card_ddcb.c:1024:6: warning: variable rc set but not
used [-Wunused-but-set-variable]
drivers/misc/genwqe/card_ddcb.c: In function genwqe_card_thread:
drivers/misc/genwqe/card_ddcb.c:1190:23: warning: variable rc set but
not used [-Wunused-but-set-variable]

Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: Hongbo Yao <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/genwqe/card_ddcb.c

···
 				queue->ddcb_daddr);
 	queue->ddcb_vaddr = NULL;
 	queue->ddcb_daddr = 0ull;
-	return -ENODEV;
+	return rc;
 
 }
 
···
  */
 static int genwqe_card_thread(void *data)
 {
-	int should_stop = 0, rc = 0;
+	int should_stop = 0;
 	struct genwqe_dev *cd = (struct genwqe_dev *)data;
 
 	while (!kthread_should_stop()) {
···
 		genwqe_check_ddcb_queue(cd, &cd->queue);
 
 		if (GENWQE_POLLING_ENABLED) {
-			rc = wait_event_interruptible_timeout(
+			wait_event_interruptible_timeout(
 				cd->queue_waitq,
 				genwqe_ddcbs_in_flight(cd) ||
 				(should_stop = kthread_should_stop()), 1);
 		} else {
-			rc = wait_event_interruptible_timeout(
+			wait_event_interruptible_timeout(
 				cd->queue_waitq,
 				genwqe_next_ddcb_ready(cd) ||
 				(should_stop = kthread_should_stop()), HZ);