perf bench futex: Fix lock-pi help string

Obvious copy/paste typo from the requeue program.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Davidlohr Bueso <dbueso@suse.de>
Link: http://lkml.kernel.org/r/1481830584-30909-1-git-send-email-dave@stgolabs.netSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/bench/futex-lock-pi.c

@@ -48,7 +48,7 @@ static const struct option options[] = {
 };
 
 static const char * const bench_futex_lock_pi_usage[] = {
-	"perf bench futex requeue <options>",
+	"perf bench futex lock-pi <options>",
 	NULL
 };