serial: 8250_pci: Make PCI class test non fatal

As has been reported the National Instruments serial cards have broken
PCI class.

The commit 7d8905d0

  ("serial: 8250_pci: Enable device after we check black list")

made the PCI class check mandatory for the case when device is listed in
a quirk list.

Make PCI class test non fatal to allow broken card be enumerated.

Fixes: 7d8905d0 ("serial: 8250_pci: Enable device after we check black list")
Cc: stable <stable@vger.kernel.org>
Reported-by: Guan Yung Tseng <guan.yung.tseng@ni.com>
Tested-by: Guan Yung Tseng <guan.yung.tseng@ni.com>
Tested-by: KHUENY.Gerhard <Gerhard.KHUENY@bachmann.info>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_pci.c

@@ -3420,6 +3420,11 @@ static int
 serial_pci_guess_board(struct pci_dev *dev, struct pciserial_board *board)
 {
 	int num_iomem, num_port, first_port = -1, i;
+	int rc;
+
+	rc = serial_pci_is_class_communication(dev);
+	if (rc)
+		return rc;
 
 	/*
 	 * Should we try to make guesses for multiport serial devices later?
@@ -3647,10 +3652,6 @@ pciserial_init_one(struct pci_dev *dev, const struct pci_device_id *ent)
 
 	board = &pci_boards[ent->driver_data];
 
-	rc = serial_pci_is_class_communication(dev);
-	if (rc)
-		return rc;
-
 	rc = serial_pci_is_blacklisted(dev);
 	if (rc)
 		return rc;