Add Sascha Hauer to .mailmap

This fixes the shortlog attribution e.g. for 106757b3



Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>