coresight: tmc-etr: Introduce the notion of IDR to ETR devices

In CPU-wide scenarios with an N:1 source/sink topology, sources share
the same sink.  In order to reuse the same sink for all sources an
IDR is needed to archive events that have already been accounted for.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Tested-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Robert Walker <robert.walker@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>