PCI: Use PCI_ERROR_RESPONSE to identify config read errors

Include PCI_ERROR_RESPONSE along with 0xFFFF and 0xFFFFFFFF in the comment
about identifying config read errors. This makes checks for config read
errors easier to find. Comment change only.

Link: https://lore.kernel.org/r/866e2db544df45af70df7e64659bf02e03998ae3.1637243717.git.naveennaidu479@gmail.com
Signed-off-by: Naveen Naidu <naveennaidu479@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/access.c

@@ -412,9 +412,9 @@ int pcie_capability_read_word(struct pci_dev *dev, int pos, u16 *val)
 	if (pcie_capability_reg_implemented(dev, pos)) {
 		ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
 		/*
-		 * Reset *val to 0 if pci_read_config_word() fails, it may
-		 * have been written as 0xFFFF if hardware error happens
-		 * during pci_read_config_word().
+		 * Reset *val to 0 if pci_read_config_word() fails; it may
+		 * have been written as 0xFFFF (PCI_ERROR_RESPONSE) if the
+		 * config read failed on PCI.
 		 */
 		if (ret)
 			*val = 0;
@@ -447,9 +447,9 @@ int pcie_capability_read_dword(struct pci_dev *dev, int pos, u32 *val)
 	if (pcie_capability_reg_implemented(dev, pos)) {
 		ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
 		/*
-		 * Reset *val to 0 if pci_read_config_dword() fails, it may
-		 * have been written as 0xFFFFFFFF if hardware error happens
-		 * during pci_read_config_dword().
+		 * Reset *val to 0 if pci_read_config_dword() fails; it may
+		 * have been written as 0xFFFFFFFF (PCI_ERROR_RESPONSE) if
+		 * the config read failed on PCI.
 		 */
 		if (ret)
 			*val = 0;