[media] pvrusb2: correctly handling failed thread run

Since kthread_run returns -ENOMEM if failed,
it needs to be checked whether it is error, not whether it is null.
Signed-off-by: NInsu Yun <wuninsu@gmail.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/usb/pvrusb2/pvrusb2-context.c

@@ -196,7 +196,7 @@ int pvr2_context_global_init(void)
 	pvr2_context_thread_ptr = kthread_run(pvr2_context_thread_func,
 					      NULL,
 					      "pvrusb2-context");
-	return (pvr2_context_thread_ptr ? 0 : -ENOMEM);
+	return IS_ERR(pvr2_context_thread_ptr) ? -ENOMEM : 0;
 }