linux-phytec-ti

MAINTAINERS: Add myself as reviewer for the PWM subsystem

I spend some time in the nearer past reviewing PWM patches. Honor this
by adding me as a reviewer.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>