PM / Runtime: Fix runtime accounting calculation error

With delta type being int, its value is made zero
for all values of now > 0x80000000.
Hence fixing it.
Signed-off-by: venu byravarasu <vbyravarasu@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

drivers/base/power/runtime.c

@@ -29,13 +29,10 @@ static int rpm_suspend(struct device *dev, int rpmflags);
 void update_pm_runtime_accounting(struct device *dev)
 {
 	unsigned long now = jiffies;
-	int delta;
+	unsigned long delta;
 
 	delta = now - dev->power.accounting_timestamp;
 
-	if (delta < 0)
-		delta = 0;
-
 	dev->power.accounting_timestamp = now;
 
 	if (dev->power.disable_depth > 0)