fix:uart demo esp下可能循环接收问题

demo/uart/main.lua

@@ -41,6 +41,9 @@ uart.on(uartid, "receive", function(id, len)
             log.info("uart", "receive", id, #s, s)
             -- log.info("uart", "receive", id, #s, s:toHex())
         end
+        if #s == len then
+            break
+        end
     until s == ""
 end)