MAINTAINERS: Remove myself as LPC32xx maintainers

I appreciate my time as a kernel maintainer for the last few years.

I am no longer working on the LPC32xx platform
and cannot commit time for support and discussions.

Signed-off-by: Sylvain Lemieux <slemieux@tycoint.com>
Acked-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>