iap 优化，避免 v8 升级失败

Signed-off-by: a1012112796 <1012112796@qq.com>

rt-thread/components/utilities/ymodem/ymodem.h

@@ -58,6 +58,11 @@ enum rym_code
 #define RYM_END_SESSION_SEND_CAN_NUM  0x07
 #endif
 
+/* how many retries were made when the error occurred */
+#ifndef RYM_MAX_ERRORS
+#define RYM_MAX_ERRORS    ((rt_size_t)20)
+#endif
+
 enum rym_stage
 {
     RYM_STAGE_NONE = 0,
@@ -105,6 +110,16 @@ struct rym_ctx
     struct rt_semaphore sem;
 
     rt_device_t dev;
+
+    /**
+     * @brief 适配 v5 iap 升级逻辑, 流程如下:
+     *
+     * 收到 EOT 后返回 ACT 'C';
+     * 收到一包空数据后返回 ACT, 正常结束 IAP
+     * 逻辑.
+     *
+     */
+    rt_bool_t v5_iap_adapt;
 };
 
 /* recv a file on device dev with ymodem session ctx.