D20284: Fix l/100 km to MPG conversion

[Nathaniel Graham]

ngraham added reviewers: Frameworks, aacid.

REPOSITORY
  R292 KUnitConversion

REVISION DETAIL
  https://phabricator.kde.org/D20284

To: madcatx, broulik, #frameworks, aacid
Cc: aacid, meven, kde-frameworks-devel, michaelh, ngraham, bruns