PCI/PM: Don't sleep at all when d3_delay or d3cold_delay is zero

msleep() still sleeps 1 jiffy even when told to sleep for zero
milliseconds.  That can end up being 1-2 milliseconds or more.  In the
cases of d3_delay and d3cold_delay, that unnecessarily increases suspend
and/or resume latencies.

Do not sleep at all for the respective cases if d3_delay is zero or
d3cold_delay is zero.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/pci/pci.c

@@ -66,6 +66,7 @@ static void pci_dev_d3_sleep(struct pci_dev *dev)
 	if (delay < pci_pm_d3_delay)
 		delay = pci_pm_d3_delay;
 
+	if (delay)
 		msleep(delay);
 }
 
@@ -827,6 +828,7 @@ static void __pci_start_power_transition(struct pci_dev *dev, pci_power_t state)
 		 * because have already delayed for the bridge.
 		 */
 		if (dev->runtime_d3cold) {
+			if (dev->d3cold_delay)
 				msleep(dev->d3cold_delay);
 			/*
 			 * When powering on a bridge from D3cold, the