coresight: perf: Add a missing call to etm_free_aux

Most error branches following the call to alloc_event_data contain a call
to etm_free_aux. This patch add a call to etm_free_aux to an error branch
that does not call it.

This issue was found with Hector.

Signed-off-by: Quentin Lambert <lambert.quentin@gmail.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>