MAINTAINERS: Add reviewer for CoreSight sub-system

On top of providing useful review and comments, Suzuki has done good work
in the CoreSight sub-system over the past couple of years.  As agreed
during a recent face-to-face converstation, adding him as a reviewer to
lessen the maintenance workload.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>