PM / QoS: return -EINVAL for bogus strings

In the current code, if the user accidentally writes a bogus command to
this sysfs file, then we set the latency tolerance to an uninitialized
variable.

Fixes: 2d984ad1 (PM / QoS: Introcuce latency tolerance device PM QoS type)
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: 3.15+ <stable@vger.kernel.org> # 3.15+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/sysfs.c

@@ -272,6 +272,8 @@ static ssize_t pm_qos_latency_tolerance_store(struct device *dev,
 			value = PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT;
 		else if (!strcmp(buf, "any") || !strcmp(buf, "any\n"))
 			value = PM_QOS_LATENCY_ANY;
+		else
+			return -EINVAL;
 	}
 	ret = dev_pm_qos_update_user_latency_tolerance(dev, value);
 	return ret < 0 ? ret : n;