serial: 8250_pci: make pciserial_detach_ports() static

Fixes the following sparse warning:

drivers/tty/serial/8250/8250_pci.c:3916:6: warning:
 symbol 'pciserial_detach_ports' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -3695,7 +3695,7 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
 }
 EXPORT_SYMBOL_GPL(pciserial_init_ports);
 
-void pciserial_detach_ports(struct serial_private *priv)
+static void pciserial_detach_ports(struct serial_private *priv)
 {
 	struct pci_serial_quirk *quirk;
 	int i;