MAINTAINERS: Update Uwe's email address, drop SIOX maintenance

MAINTAINERS: Update Uwe's email address, drop SIOX maintenance

In the context of changing my career path, my Pengutronix email address
will soon stop to be available to me. Update the PWM maintainer entry to
my kernel.org identity.

I drop my co-maintenance of SIOX. Thorsten will continue to care for
it with the support of the Pengutronix kernel team.

Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Acked-by: Thorsten Scherer <t.scherer@eckelmann.de>
Link: https://lore.kernel.org/r/20240424212626.603631-2-ukleinek@kernel.org
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>