Missing boards added to Maixduino core and K210 support added to TFT_eSPI

Hi there!

Hope it will be useful:
[https://github.com/sipeed/Maixduino/pull/99](http://PR with boards update)
[https://github.com/Bodmer/TFT_eSPI/pull/815](http://PR for K210 support in TFT_eSPI library)

All credits go to https://qiita.com/fukuebiz !