ARM 裸机移植的yaffs文件系统。由于yaffs每次启动都会扫描所有nand，所以需要比较长的时间，为了加快启动速度，所以在这里暂时只配了2M-ARM bare transplant yaffs file system. Because every time you start yaffs will scan all nand, so they need a relatively long time, in order to speed up the startup speed, so he