PCI/PM: Simplify pci_set_power_state()

Check for the PCI_DEV_FLAGS_NO_D3 quirk early, before calling
__pci_start_power_transition().  This way all the cases where we don't need
to do anything at all are checked up front.

This doesn't fix anything because if the caller requested D3hot or D3cold,
__pci_start_power_transition() is a no-op.  But calling it is pointless and
makes the code harder to analyze.

Link: https://lore.kernel.org/r/20191101204558.210235-4-helgaas@kernel.orgSigned-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/pci/pci.c

@@ -1117,8 +1117,6 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
 	if (dev->current_state == state)
 		return 0;
 
-	__pci_start_power_transition(dev, state);
-
 	/*
 	 * This device is quirked not to be put into D3, so don't put it in
 	 * D3
@@ -1126,6 +1124,8 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
 	if (state >= PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
 		return 0;
 
+	__pci_start_power_transition(dev, state);
+
 	/*
 	 * To put device in D3cold, we put device into D3hot in native
 	 * way, then put device into D3cold with platform ops