wince pxa270 基于ds1672 的rtc程序-ds1672 rtc

基于YF PXA255开发板的eboot代码，增加了使用SD卡下载镜像的功能，下载速度快，25M的镜像仅需30s，可以用于省略网口的小型化开发；同时增加了eboot启动时读取外接I2C接口RTC时间的功能-YF PXA255 development board-based eboot code. The use of SD card to download the image file function is added with fast speed: 25M image only 30s,