x86: fix nmi_watchdog=2 on Pentium-D CPUs

implement nmi_watchdog=2 on this class of CPUs:

  cpu family      : 15
  model           : 6
  model name      : Intel(R) Pentium(R) D CPU 3.00GHz

the watchdog's ->setup() method is safe anyway, so if the CPU
cannot support it we'll bail out safely.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perfctr-watchdog.c

@@ -652,9 +652,6 @@ static void probe_nmi_watchdog(void)
 			wd_ops = &p6_wd_ops;
 			break;
 		case 15:
-			if (boot_cpu_data.x86_model > 0x4)
-				return;
-
 			wd_ops = &p4_wd_ops;
 			break;
 		default: