PCI: Check for the existence of 'dev.of_node' before calling of_platform_populate()

Commit 50b040ef ("PCI/pwrctl: only call of_platform_populate() if
CONFIG_OF is enabled") added the CONFIG_OF guard for the
of_platform_populate() API.  But it missed the fact that the CONFIG_OF
platforms can also run on ACPI without devicetree (so dev.of_node will
be NULL).  In those cases, of_platform_populate() will fail with below
error messages as seen on the Ampere Altra box:

  pci 000c:00:01.0: failed to populate child OF nodes (-22)
  pci 000c:00:02.0: failed to populate child OF nodes (-22)

Fix this by checking for the existence of 'dev.of_node' before calling
the of_platform_populate() API.  This also warrants the removal of
CONFIG_OF check, since dev_of_node() helper will return NULL if
CONFIG_OF is not enabled.

While at it, let's also use dev_of_node() to pass device OF node pointer
to of_platform_populate().

Fixes: 50b040ef ("PCI/pwrctl: only call of_platform_populate() if CONFIG_OF is enabled")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/linux-arm-msm/CAHk-=wjcO_9dkNf-bNda6bzykb5ZXWtAYA97p7oDsXPHmMRi6g@mail.gmail.comReviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/pci/bus.c

@@ -356,8 +356,8 @@ void pci_bus_add_device(struct pci_dev *dev)
 
 	pci_dev_assign_added(dev, true);
 
-	if (IS_ENABLED(CONFIG_OF) && pci_is_bridge(dev)) {
-		retval = of_platform_populate(dev->dev.of_node, NULL, NULL,
+	if (dev_of_node(&dev->dev) && pci_is_bridge(dev)) {
+		retval = of_platform_populate(dev_of_node(&dev->dev), NULL, NULL,
 					      &dev->dev);
 		if (retval)
 			pci_err(dev, "failed to populate child OF nodes (%d)\n",