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>

include/pthread.h

@@ -368,6 +368,8 @@ struct pthread_barrier_s
 {
   sem_t        sem;
   unsigned int count;
+  unsigned int wait_count;
+  mutex_t      mutex;
 };
 
 #ifndef __PTHREAD_BARRIER_T_DEFINED