perf_counter, x86: add default path to cpu detection

This quits hw counter initialization immediately if no cpu is
detected.

[ Impact: cleanup ]
Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1241002046-8832-4-git-send-email-robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_counter.c

@@ -997,6 +997,8 @@ void __init init_hw_perf_counters(void)
 	case X86_VENDOR_AMD:
 		pmc_ops = pmc_amd_init();
 		break;
+	default:
+		return;
 	}
 	if (!pmc_ops)
 		return;