perf cgroup: Make evlist__find_cgroup() more compact

By taking advantage that __get() routines return the pointer to the
object for which a reference count is being get.

Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: https://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/cgroup.c

···
 static struct cgroup *evlist__find_cgroup(struct perf_evlist *evlist, const char *str)
 {
 	struct perf_evsel *counter;
-	struct cgroup *cgrp = NULL;
 	/*
 	 * check if cgrp is already defined, if so we reuse it
 	 */
 	evlist__for_each_entry(evlist, counter) {
 		if (!counter->cgrp)
 			continue;
-		if (!strcmp(counter->cgrp->name, str)) {
-			cgrp = cgroup__get(counter->cgrp);
-			break;
-		}
+		if (!strcmp(counter->cgrp->name, str))
+			return cgroup__get(counter->cgrp);
 	}
 
-	return cgrp;
+	return NULL;
 }
 
 static struct cgroup *cgroup__new(const char *name)