coresight: etm3x: Release CLAIM tag when operated from perf

This patch deals with the release of the CLAIM tag when the ETM is
operated from perf.  Otherwise the tag is left asserted and subsequent
requests to use the device fail.

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