Add Uwe Kleine-König to .mailmap

There are a few commits that misencoded my name (or used "oe" instead of
"ö").  So add a correct version to .mailmap.

Signed-off-by: Uwe Kleine-König <ukleinek@informatik.uni-freiburg.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>