pthread: remove enter_critical_section in pthread_barrier_wait

reason:
We decouple semcount from business logic by using an independent counting variable,
which allows us to remove critical sections in many cases.

Signed-off-by: hujun5 <hujun5@xiaomi.com>

libs/libc/pthread/pthread_barrierinit.c

@@ -87,6 +87,8 @@ int pthread_barrier_init(FAR pthread_barrier_t *barrier,
     {
       sem_init(&barrier->sem, 0, 0);
       barrier->count = count;
+      barrier->wait_count = 0;
+      nxmutex_init(&barrier->mutex);
     }
 
   return ret;