mutex: remove mutex trylock holder check

The standard describes trylock as follows, trylock should never cause the system to stop running:

The pthread_mutex_trylock() function shall be equivalent to
pthread_mutex_lock(), except that if the mutex object referenced by
mutex is currently locked (by any thread, including the current thread),
the call shall return immediately.

https://linux.die.net/man/3/pthread_mutex_trylock

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

libs/libc/misc/lib_mutex.c

@@ -241,7 +241,6 @@ int nxmutex_trylock(FAR mutex_t *mutex)
 {
   int ret;
 
-  DEBUGASSERT(!nxmutex_is_hold(mutex));
   ret = nxsem_trywait(&mutex->sem);
   if (ret < 0)
     {