PCI: Add device even if driver attach failed

device_attach() returning failure indicates a driver error while trying to
probe the device. In such a scenario, the PCI device should still be added
in the system and be visible to the user.

When device_attach() fails, merely warn about it and keep the PCI device in
the system.

This partially reverts ab1a187b ("PCI: Check device_attach() return
value always").

Link: https://lore.kernel.org/r/20200706233240.3245512-1-rajatja@google.comSigned-off-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org	# v4.6+

drivers/pci/bus.c

@@ -322,12 +322,8 @@ void pci_bus_add_device(struct pci_dev *dev)
 
 	dev->match_driver = true;
 	retval = device_attach(&dev->dev);
-	if (retval < 0 && retval != -EPROBE_DEFER) {
+	if (retval < 0 && retval != -EPROBE_DEFER)
 		pci_warn(dev, "device attach failed (%d)\n", retval);
-		pci_proc_detach_device(dev);
-		pci_remove_sysfs_dev_files(dev);
-		return;
-	}
 
 	pci_dev_assign_added(dev, true);
 }