libc: Call pthread_exit in user-space by up_pthread_exit

Drop to user-space in kernel/protected build with up_pthread_exit,
now all pthread_cleanup functions executed in user mode.

* A new syscall SYS_pthread_exit added
* A new tcb flag TCB_FLAG_CANCEL_DOING added
* up_pthread_exit implemented for riscv/arm arch

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

libs/libc/pthread/pthread_create.c

@@ -87,5 +87,5 @@ int pthread_create(FAR pthread_t *thread, FAR const pthread_attr_t *attr,
                    pthread_startroutine_t pthread_entry, pthread_addr_t arg)
 {
   return nx_pthread_create(pthread_startup, thread, attr, pthread_entry,
-                           arg);
+                           arg, pthread_exit);
 }

libs/libc/pthread/pthread_exit.c

@@ -40,7 +40,7 @@
  *   Terminate execution of a thread started with pthread_create.
  *
  * Input Parameters:
- *   exit_value
+ *   exit_value - The pointer of the pthread_exit parameter
  *
  * Returned Value:
  *   None