emummc: support for 8.1.0

git subrepo clone --branch=develop https://github.com/m4xw/emuMMC emummc ...

subrepo:
  subdir:   "emummc"
  merged:   "e72e8f1c"
upstream:
  origin:   "https://github.com/m4xw/emuMMC"
  branch:   "develop"
  commit:   "e72e8f1c"
git-subrepo:
  version:  "0.4.0"
  origin:   "https://github.com/ingydotnet/git-subrepo"
  commit:   "5d6aba9"