fix build without SCHED_MULTITHREADED defined (issue #6719)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@12878 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -7919,7 +7919,9 @@ static void *iax2_process_thread(void *data)
 		case IAX_IOSTATE_SCHEDREADY:
 			thread->actions++;
 			thread->iostate = IAX_IOSTATE_PROCESSING;
+#ifdef SCHED_MULTITHREAD
 			thread->schedfunc(thread->scheddata);
+#endif		
 			break;
 		}
 		time(&thread->checktime);