perf evlist: Directly return instead of using local ret variable

Addresses this coccinelle warning:

./tools/perf/util/evlist.c:1333:5-8: Unneeded variable: "err". Return
"- ENOMEM" on line 1358

Signed-off-by: Haowen Bai <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Andrii Nakryiko <[e-mail]>
Cc: Daniel Borkmann <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: John Fastabend <[e-mail]>
Cc: KP Singh <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Martin KaFai Lau <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Song Liu <[e-mail]>
Cc: Yonghong Song <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/evlist.c

···
 {
 	struct perf_cpu_map *cpus;
 	struct perf_thread_map *threads;
-	int err = -ENOMEM;
 
 	/*
 	 * Try reading /sys/devices/system/cpu/online to get
···
 out_put:
 	perf_cpu_map__put(cpus);
 out:
-	return err;
+	return -ENOMEM;
 }
 
 int evlist__open(struct evlist *evlist)