USB: serial: iuu_phoenix: fix NULL-deref at open

Fix NULL-pointer dereference at open should the device lack a bulk-in or
bulk-out endpoint:

Unable to handle kernel NULL pointer dereference at virtual address 00000030
...
PC is at iuu_open+0x78/0x59c [iuu_phoenix]

Fixes: 07c3b1a10016 ("USB: remove broken usb-serial num_endpoints
check")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/iuu_phoenix.c

@@ -68,6 +68,16 @@ struct iuu_private {
 	u32 clk;
 };
 
+static int iuu_attach(struct usb_serial *serial)
+{
+	unsigned char num_ports = serial->num_ports;
+
+	if (serial->num_bulk_in < num_ports || serial->num_bulk_out < num_ports)
+		return -ENODEV;
+
+	return 0;
+}
+
 static int iuu_port_probe(struct usb_serial_port *port)
 {
 	struct iuu_private *priv;
@@ -1196,6 +1206,7 @@ static struct usb_serial_driver iuu_device = {
 	.tiocmset = iuu_tiocmset,
 	.set_termios = iuu_set_termios,
 	.init_termios = iuu_init_termios,
+	.attach = iuu_attach,
 	.port_probe = iuu_port_probe,
 	.port_remove = iuu_port_remove,
 };