perf probe: Fix concat_probe_trace_events

'*ntevs' contains number of elements present in 'tevs' array. If there
are no elements in array, 'tevs2' can be directly assigned to 'tevs'
without allocating more space. So the condition should be  '*ntevs == 0'
not  'ntevs == 0'.
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 42bba263 ("perf probe: Allow wildcard for cached events")
Link: http://lkml.kernel.org/r/20170308065908.4128-1-ravi.bangoria@linux.vnet.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-event.c

@@ -3048,7 +3048,7 @@ concat_probe_trace_events(struct probe_trace_event **tevs, int *ntevs,
 	struct probe_trace_event *new_tevs;
 	int ret = 0;
 
-	if (ntevs == 0) {
+	if (*ntevs == 0) {
 		*tevs = *tevs2;
 		*ntevs = ntevs2;
 		*tevs2 = NULL;