Ensure MAVLink app has enough stack space

src/modules/mavlink/mavlink_main.cpp

@@ -1634,7 +1634,7 @@ Mavlink::start(int argc, char *argv[])
 	task_spawn_cmd(buf,
 		       SCHED_DEFAULT,
 		       SCHED_PRIORITY_DEFAULT,
-		       2700,
+		       2900,
 		       (main_t)&Mavlink::start_helper,
 		       (const char **)argv);