perf cs-etm: Suppress printing when resetting decoder

The decoder is quite noisy when being reset. In a future commit,
dump-raw-trace will use a code path that resets the decoder rather than
creating a new one, so printing has to be suppressed to not flood the
output.

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: James Clark <james.clark@arm.com>