perf tests: Initialize sa.sa_flags

The sa_flags field is not being initialized, so a garbage value is being
passed to sigaction.  Initialize it to zero.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1456923322-29697-1-git-send-email-colin.king@canonical.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/x86/tests/rdpmc.c

@@ -103,6 +103,7 @@ static int __test__rdpmc(void)
 
 	sigfillset(&sa.sa_mask);
 	sa.sa_sigaction = segfault_handler;
+	sa.sa_flags = 0;
 	sigaction(SIGSEGV, &sa, NULL);
 
 	fd = sys_perf_event_open(&attr, 0, -1, -1,