Simplify Bitaxe OLED display

[skot]

I'm starting to think we're showing too much on the bitaxe OLED. It's a really small screen that gets cluttered easily. I think we should focus on showing the absolute minimum amount of data;

• hashrate
• temperature
• best difficulty
  and then maybe a secondary screen that only comes up when you press boot;
• IP address
• ?

All of the rest of the data that we currently show is useful, but it's better shown on the dashboard where there is plenty of room.

[skot]

Something like this

I created a LVGL Pro XML file to do this if anyone can figure out that madness; https://github.com/skot/bitaxe-oled