Revert "mavlink: revert stack size 2048 to fix suspending in HIL mode"

This reverts commit eb177def14.

src/modules/mavlink/mavlink.c

@@ -773,7 +773,7 @@ int mavlink_main(int argc, char *argv[])
 		mavlink_task = task_spawn_cmd("mavlink",
 					  SCHED_DEFAULT,
 					  SCHED_PRIORITY_DEFAULT,
-					  2048,
+					  1200,
 					  mavlink_thread_main,
 					  (const char **)argv);