PCI/ERR: Recognize disconnected devices in report_error_detected()

When a device is already unplugged by pciehp by the time the AER handler is
invoked, the PCIe device will already be in the pci_channel_io_perm_failure
state.  In that case simply return PCI_ERS_RESULT_DISCONNECT instead of
trying to do a state transition that will fail.

Also untangle the state transition failure from the lack of methods to
improve the debugging output in case it happens again.

Link: https://lore.kernel.org/r/20220601074024.3481035-1-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

drivers/pci/pcie/err.c

@@ -55,9 +55,13 @@ static int report_error_detected(struct pci_dev *dev,
 
 	device_lock(&dev->dev);
 	pdrv = dev->driver;
-	if (!pci_dev_set_io_state(dev, state) ||
-		!pdrv ||
-		!pdrv->err_handler ||
+	if (pci_dev_is_disconnected(dev)) {
+		vote = PCI_ERS_RESULT_DISCONNECT;
+	} else if (!pci_dev_set_io_state(dev, state)) {
+		pci_info(dev, "can't recover (state transition %u -> %u invalid)\n",
+			dev->error_state, state);
+		vote = PCI_ERS_RESULT_NONE;
+	} else if (!pdrv || !pdrv->err_handler ||
 		   !pdrv->err_handler->error_detected) {
 		/*
 		 * If any device in the subtree does not have an error_detected