[shell] set prompt mode is default enable.

components/finsh/shell.c

@@ -34,6 +34,7 @@
  * 2011-02-23     Bernard      fix variable section end issue of finsh shell
  *                             initialization when use GNU GCC compiler.
  * 2016-11-26     armink       add password authentication
+ * 2018-07-02     aozima       add custome prompt support.
  */
 
 #include <rthw.h>
@@ -853,6 +854,7 @@ int finsh_system_init(void)
 #endif /* RT_USING_HEAP */
 
     rt_sem_init(&(shell->rx_sem), "shrx", 0, 0);
+    finsh_set_prompt_mode(1);
 
     if (tid != NULL && result == RT_EOK)
         rt_thread_startup(tid);