Merge branch 'feature/esptool_v2.8_v4.0' into 'release/v4.0'

esptool: Bump to v2.8 release (v4.0)

See merge request espressif/esp-idf!6460
This commit is contained in:
Jiang Jiang Jian
2019-10-25 11:38:09 +08:00