修复ringblk_buf在不使用动态内存时报错的问题

components/drivers/src/ringblk_buf.c

@@ -44,6 +44,8 @@ void rt_rbb_init(rt_rbb_t rbb, rt_uint8_t *buf, rt_size_t buf_size, rt_rbb_blk_t
 }
 RTM_EXPORT(rt_rbb_init);
 
+#ifdef RT_USING_HEAP
+
 /**
  * ring block buffer object create
  *
@@ -102,6 +104,8 @@ void rt_rbb_destroy(rt_rbb_t rbb)
 }
 RTM_EXPORT(rt_rbb_destroy);
 
+#endif
+
 static rt_rbb_blk_t find_empty_blk_in_set(rt_rbb_t rbb)
 {
     rt_size_t i;