acpi_pm: Clear pmtmr_ioport if acpi_pm initialization fails

If the acpi pm timer throws invalid data, clear pmtmr_ioport
so the pm timer won't accidentally be used.

This was found when using Xen where there is a acpi pm reported,
but gives bogus values, and other code was continuing to try
to use the pm timer after the initialization failed.

[jstultz: Catch additional failure and reword changelog message. ]

Signed-off-by: Konrad Rzeszutek Wilk <[e-mail]>
Signed-off-by: John Stultz <[e-mail]>
LKML-Reference: <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>

drivers/clocksource/acpi_pm.c

···
 			printk(KERN_INFO "PM-Timer had inconsistent results:"
 			       " 0x%#llx, 0x%#llx - aborting.\n",
 			       value1, value2);
+			pmtmr_ioport = 0;
 			return -EINVAL;
 		}
 		if (i == ACPI_PM_READ_CHECKS) {
 			printk(KERN_INFO "PM-Timer failed consistency check "
 			       " (0x%#llx) - aborting.\n", value1);
+			pmtmr_ioport = 0;
 			return -ENODEV;
 		}
 	}
 
-	if (verify_pmtmr_rate() != 0)
+	if (verify_pmtmr_rate() != 0){
+		pmtmr_ioport = 0;
 		return -ENODEV;
+	}
 
 	return clocksource_register_hz(&clocksource_acpi_pm,
 						PMTMR_TICKS_PER_SEC);