perf pmu: Fix a potential memory leak in perf_pmu__lookup()

The commit in Fixes has reordered some code, but missed an error handling
path.

'goto err' now, in order to avoid a memory leak in case of error.

Fixes: f63a536f03a2 ("perf pmu: Merge JSON events with sysfs at load time")
Signed-off-by: Christophe JAILLET <[e-mail]>
Reviewed-by: Ian Rogers <[e-mail]>
Cc: [e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/9538b2b634[e-mail]

tools/perf/util/pmu.c

···
 	 * type value and format definitions. Load both right
 	 * now.
 	 */
-	if (pmu_format(pmu, dirfd, name)) {
-		free(pmu);
-		return NULL;
-	}
+	if (pmu_format(pmu, dirfd, name))
+		goto err;
+
 	pmu->is_core = is_pmu_core(name);
 	pmu->cpus = pmu_cpumask(dirfd, name, pmu->is_core);