sched: Don't duplicate caller file handler when creating kernel thread

kernel thread should have only the starndard file i/o just like idle thread

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

sched/task/task_init.c

@@ -105,7 +105,15 @@ int nxtask_init(FAR struct task_tcb_s *tcb, const char *name, int priority,
 
   /* Associate file descriptors with the new task */
 
+  if (ttype == TCB_FLAG_TTYPE_KERNEL)
+    {
+      ret = group_setupidlefiles(tcb);
+    }
+  else
+    {
       ret = group_setuptaskfiles(tcb);
+    }
+
   if (ret < 0)
     {
       goto errout_with_group;