sched: nxtask_start should call entry point directly for kernel thread

since nxtask_startup will initialize c++ global variables which shouldn't
be done inside the kernel thread

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

sched/task/task_start.c

@@ -134,18 +134,18 @@ void nxtask_start(void)
    * we have to switch to user-mode before calling the task.
    */
 
-#ifndef CONFIG_BUILD_FLAT
-  if ((tcb->cmn.flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_KERNEL)
+  if ((tcb->cmn.flags & TCB_FLAG_TTYPE_MASK) == TCB_FLAG_TTYPE_KERNEL)
     {
-      up_task_start(tcb->cmn.entry.main, argc, tcb->argv);
+      exitcode = tcb->cmn.entry.main(argc, tcb->argv);
     }
   else
     {
-      exitcode = tcb->cmn.entry.main(argc, tcb->argv);
-    }
+#ifdef CONFIG_BUILD_FLAT
+      nxtask_startup(tcb->cmn.entry.main, argc, tcb->argv);
 #else
-  nxtask_startup(tcb->cmn.entry.main, argc, tcb->argv);
+      up_task_start(tcb->cmn.entry.main, argc, tcb->argv);
 #endif
+    }
 
   /* Call exit() if/when the task returns */