perf evlist: Directly return instead of using local ret variable

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 <baihaowen@meizu.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: http://lore.kernel.org/lkml/1648432532-23151-1-git-send-email-baihaowen@meizu.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>