perf coresight: Remove superfluous check before use

perf coresight: Remove superfluous check before use

The cs_etm_evsel variable is guaranteed to be set at this point in
cs_etm_recording_options().

Signed-off-by: Kim Phillips <kim.phillips@arm.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20170615125521.80cc128dc856bc1f2e61b730@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>