【doc】update completion.c comments
【doc】update completion.c comments

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