MAINTAINERS: Remove myself as a Arm CoreSight reviewer

I haven't done any meaningful work for a long while on Arm CoreSight and
it's unlikely I'll be able to do related work in the future.

Remove myself from the Arm CoreSight "Reviewers" list.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230904092311.389112-1-leo.yan@linaro.org