Whatever dumbass wrote sio_pci.c didn't include a detach method.

Wearing said pointy hat, correct the oversight and hope nobody
notices.

# this should make xircom modems happier to detach once other bugs with
# the cardbus layer are fixed.

Noticed by: scottl
Conical Hat to: imp

sys/dev/sio/sio_pci.c

@@ -50,6 +50,7 @@ static device_method_t sio_pci_methods[] = {
 	/* Device interface */
 	DEVMETHOD(device_probe,		sio_pci_probe),
 	DEVMETHOD(device_attach,	sio_pci_attach),
+	DEVMETHOD(device_detach,	siodetach),
 
 	{ 0, 0 }
 };