Update Readme OSD infomations

I checked the source code and found that all the names of "Receiving packets statistics" should have either ​​".delta"​​ or ​​".total"​​ appended to them; otherwise, they won't be displayed correctly. 

For example:

Current names: `wfbcli.rx.packets.all`
Should be modified to : `wfbcli.rx.packets.all.delta`  or `wfbcli.rx.packets.all.total`