MAINTAINERS: add personal addresses for Sascha and Uwe

The idea behind using kernel@pengutronix.de (i.e. the mail alias for the
kernel people at Pengutronix) as email address was to have a backup when
a given developer is on vacation or run over by a bus. Make this more
explicit by adding the alias as reviewer and use the personal address
for Sascha and me.

Link: http://lkml.kernel.org/r/20180413083312.11213-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>