1、【修改】FreeModbus主机释放资源部分源码，解决了偶尔会出现获取信号量失败的Bug。

Signed-off-by: armink <armink.ztl@gmail.com>

FreeModbus/port/portevent_m.c

@@ -91,8 +91,7 @@ BOOL xMBMasterRunResTake( LONG lTimeOut )
  */
 void vMBMasterRunResRelease( void )
 {
-	/* Clear up resource when need release resource. */
-	rt_sem_control(&xMasterRunRes, RT_IPC_CMD_RESET, 0);
+	/* release resource */
 	rt_sem_release(&xMasterRunRes);
 }