Documentation: coresight: Update coresight configuration docs

Update the CoreSight System Configuration document to cover the
use of loadable modules to add configurations and features
to the system.

Signed-off-by: Mike Leach <mike.leach@linaro.org>
Link: https://lore.kernel.org/r/20211124200038.28662-7-mike.leach@linaro.org


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>