USB: serial: allow subdrivers to modify port-endpoint mapping

Allow subdrivers to modify the port-endpoint mapping by passing the
endpoint descriptors to calc_num_ports.

The callback can now also be used to verify that the required endpoints
exists and abort probing otherwise.

This will allow us to get rid of a few hacks in subdrivers that are
already modifying the port-endpoint mapping (or aborting probe due to
missing endpoints), but only after the port structures have been setup.

Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/mxuport.c

@@ -946,7 +946,8 @@ out:
  * Determine how many ports this device has dynamically.  It will be
  * called after the probe() callback is called, but before attach().
  */
-static int mxuport_calc_num_ports(struct usb_serial *serial)
+static int mxuport_calc_num_ports(struct usb_serial *serial,
+					struct usb_serial_endpoints *epds)
 {
 	unsigned long features = (unsigned long)usb_get_serial_data(serial);