perf tools: Fix multi-counter stat bug caused by incorrect reading of perf.data file header

Brice Goglin reported that only the first result from a
multi-counter perf record --stat run is accurate, the
rest looks bogus.

A silly mistake made us re-read the first attribute for
every recorded attribute.

Reported-by: Brice Goglin <Brice.Goglin@inria.fr>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Brice Goglin <Brice.Goglin@inria.fr>
Cc: paulus@samba.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/header.c

@@ -213,9 +213,10 @@ struct perf_header *perf_header__read(int fd)
 
 	for (i = 0; i < nr_attrs; i++) {
 		struct perf_header_attr *attr;
-		off_t tmp = lseek(fd, 0, SEEK_CUR);
+		off_t tmp;
 
 		do_read(fd, &f_attr, sizeof(f_attr));
+		tmp = lseek(fd, 0, SEEK_CUR);
 
 		attr = perf_header_attr__new(&f_attr.attr);