MAINTAINERS: Add CoreSight header files

Adding CoreSight headers to the list of supported files so that maintainers
can be notified when changes are submitted.

Link: https://lore.kernel.org/r/20210326155431.2011889-1-mathieu.poirier@linaro.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20210407160007.418053-5-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>