perf record: Fix s390 undefined record__auxtrace_init() return value

Command 'perf record' calls:

  cmd_report()
    record__auxtrace_init()
       auxtrace_record__init()

On s390 function auxtrace_record__init() returns random return value due
to missing initialization.

This sometime causes 'perf record' to exit immediately without error
message and creating a perf.data file.

Fix this by setting error the return code to zero before returning from
platform specific functions which may not set the error code in call
cases.

Signed-off-by: Thomas Richter <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Hendrik Brueckner <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/arch/s390/util/auxtrace.c

@@ -87,6 +87,7 @@ struct auxtrace_record *auxtrace_record__init(struct perf_evlist *evlist,
 	struct perf_evsel *pos;
 	int diagnose = 0;
 
+	*err = 0;
 	if (evlist->nr_entries == 0)
 		return NULL;