perf diff: Fix error return value in __cmd_diff()

An appropriate return value should be set on the failed path.

Fixes: 2a09a84c ("perf diff: Support hot streams comparison")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20201124103652.438-1-thunder.leizhen@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-diff.c

@@ -1222,8 +1222,10 @@ static int __cmd_diff(void)
 		if (compute == COMPUTE_STREAM) {
 			d->evlist_streams = evlist__create_streams(
 						d->session->evlist, 5);
-			if (!d->evlist_streams)
+			if (!d->evlist_streams) {
+				ret = -ENOMEM;
 				goto out_delete;
+			}
 		}
 	}