[修复] 修复msh无法配置超过256字节的长度输入 | Fixed MSH unable to configure input length exceeding 256 bytes

components/finsh/shell.h

@@ -79,8 +79,8 @@ struct finsh_shell
 #endif
 
     char line[FINSH_CMD_SIZE];
-    rt_uint8_t line_position;
-    rt_uint8_t line_curpos;
+    rt_uint16_t line_position;
+    rt_uint16_t line_curpos;
 
 #ifndef RT_USING_POSIX
     rt_device_t device;