[media] saa7164: fix return value check in saa7164_initdev()

In case of error, the function kthread_run() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check
should be replaced with IS_ERR().
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/pci/saa7164/saa7164-core.c

@@ -1354,9 +1354,11 @@ static int saa7164_initdev(struct pci_dev *pci_dev,
 		if (fw_debug) {
 			dev->kthread = kthread_run(saa7164_thread_function, dev,
 				"saa7164 debug");
-			if (!dev->kthread)
+			if (IS_ERR(dev->kthread)) {
+				dev->kthread = NULL;
 				printk(KERN_ERR "%s() Failed to create "
 					"debug kernel thread\n", __func__);
+			}
 		}
 
 	} /* != BOARD_UNKNOWN */