Generic ports for RK3288/RK3399/MT8173/MT8183 chromebooks

There are several disadvantages for this:

• We are approaching kernel partition size limit;
• We install hwids-udev on some devices which don't need it;
• We install some firmware on some devices which don't need it;

But in my opinion it is still worth doing it

TODO:

• update wiki;
• test veyron;
• test gru;
• test oak;
• test kukui;
• test upgrading from an old installation.
  • tested with pmbootstrap sideload device-google-kukui