PM / QoS: fix wrong error-checking condition

dev_pm_qos_add_request() can return 0, 1, or a negative error code,
therefore the correct error test is "if (error < 0)." Checking just for
non-zero return code leads to erroneous setting of the req->dev pointer
to NULL, which then leads to a repeated call to
dev_pm_qos_add_ancestor_request() in st1232_ts_irq_handler(). This in turn
leads to an Oops, when the I2C host adapter is unloaded and reloaded again
because of the inconsistent state of its QoS request list.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/qos.c

@@ -451,7 +451,7 @@ int dev_pm_qos_add_ancestor_request(struct device *dev,
 	if (ancestor)
 		error = dev_pm_qos_add_request(ancestor, req, value);
 
-	if (error)
+	if (error < 0)
 		req->dev = NULL;
 
 	return error;