Stage 1 app开始执行，首先作系统初始化（汇编语言写）；然后做stage 1 app相关初始化，包括获取配置参数、初始化中断和串口、初始化LCD和显示logo，初始化stage 1 app命令等；然后进入stage 1 app命令行或者自动加uboot。-Stage 1 the app is started, the first for the system initialization (assembly language) and then do the stage 1 the a