serial: 8250_pci: handle FL_NOIRQ board flag

In commit 8428413b ("serial: 8250_pci: Implement MSI(-X) support")
the way the irq gets allocated was changed. With that change the
handling FL_NOIRQ got lost. Restore the old behaviour.

Fixes: 8428413b ("serial: 8250_pci: Implement MSI(-X) support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Link: https://lore.kernel.org/r/20210527095529.26281-1-christian.gmeiner@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -3958,6 +3958,9 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
 	uart.port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ;
 	uart.port.uartclk = board->base_baud * 16;
 
+	if (board->flags & FL_NOIRQ) {
+		uart.port.irq = 0;
+	} else {
 		if (pci_match_id(pci_use_msi, dev)) {
 			dev_dbg(&dev->dev, "Using MSI(-X) interrupts\n");
 			pci_set_master(dev);
@@ -3973,6 +3976,8 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
 		}
 
 		uart.port.irq = pci_irq_vector(dev, 0);
+	}
+
 	uart.port.dev = &dev->dev;
 
 	for (i = 0; i < nr_ports; i++) {