perf tools: Modify error code for when perf_session__new() fails

Because perf_session__new() can fail for more reasons than just ENOMEM,
modify error code(ENOMEM or EINVAL) to -1.

Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1411522417-9917-1-git-send-email-treeze.taeung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 190d0b6..a3ce19f 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -683,7 +683,7 @@
 		d->session = perf_session__new(&d->file, false, &tool);
 		if (!d->session) {
 			pr_err("Failed to open %s\n", d->file.path);
-			ret = -ENOMEM;
+			ret = -1;
 			goto out_delete;
 		}