[bsp][qemu-vexpress-a9] 完善readme
[bsp][qemu-vexpress-a9] 完善readme

ArdaFu/rt-thread,weety/rt-thread,geniusgogo/rt-thread,RT-Thread/rt-thread,geniusgogo/rt-thread,nongxiaoming/rt-thread,nongxiaoming/rt-thread,nongxiaoming/rt-thread,geniusgogo/rt-thread,RT-Thread/rt-thread,ArdaFu/rt-thread,weety/rt-thread,hezlog/rt-thread,nongxiaoming/rt-thread,weety/rt-thread,ArdaFu/rt-thread,geniusgogo/rt-thread,ArdaFu/rt-thread,geniusgogo/rt-thread,geniusgogo/rt-thread,nongxiaoming/rt-thread,ArdaFu/rt-thread,weety/rt-thread,hezlog/rt-thread,geniusgogo/rt-thread,hezlog/rt-thread,ArdaFu/rt-thread,RT-Thread/rt-thread,ArdaFu/rt-thread,weety/rt-thread,nongxiaoming/rt-thread,hezlog/rt-thread,hezlog/rt-thread,hezlog/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,weety/rt-thread,RT-Thread/rt-thread,weety/rt-thread,hezlog/rt-thread,nongxiaoming/rt-thread,RT-Thread/rt-thread