MAVLink: Increased stack size

This is needed for MAVLink shell and UAVCAN.

src/modules/mavlink/mavlink_main.cpp

@@ -2690,7 +2690,7 @@ Mavlink::start(int argc, char *argv[])
 	px4_task_spawn_cmd(buf,
 			   SCHED_DEFAULT,
 			   SCHED_PRIORITY_DEFAULT,
-			   2496 + MAVLINK_NET_ADDED_STACK,
+			   2896 + MAVLINK_NET_ADDED_STACK,
 			   (px4_main_t)&Mavlink::start_helper,
 			   (char *const *)argv);