perf tests kvm: Avoid leaving perf.data.guest file around

Ensure the perf.data output when checking permissions is written to
/dev/null so that it isn't left in the directory the test is run.

Fixes: b582615 ("perf test kvm: Add some basic perf kvm test coverage")
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Author: captain5050

tools/perf/tests/shell/kvm.sh

@@ -118,7 +118,7 @@ setup_qemu() {
 		skip "/dev/kvm not accessible"
 	fi
 
-	if ! perf kvm stat record -a sleep 0.01 >/dev/null 2>&1; then
+	if ! perf kvm stat record -o /dev/null -a sleep 0.01 >/dev/null 2>&1; then
 		skip "No permission to record kvm events"
 	fi