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

Fix NULL-pointer dereference when initialising URBs at open should a
non-EPIC device lack a bulk-in or interrupt-in endpoint.

Unable to handle kernel NULL pointer dereference at virtual address 00000028
...
PC is at edge_open+0x24c/0x3e8 [io_edgeport]

Note that the EPIC-device probe path has the required sanity checks so
this makes those checks partially redundant.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/io_edgeport.c

@@ -2751,6 +2751,11 @@ static int edge_startup(struct usb_serial *serial)
 					EDGE_COMPATIBILITY_MASK1,
 					EDGE_COMPATIBILITY_MASK2 };
 
+	if (serial->num_bulk_in < 1 || serial->num_interrupt_in < 1) {
+		dev_err(&serial->interface->dev, "missing endpoints\n");
+		return -ENODEV;
+	}
+
 	dev = serial->dev;
 
 	/* create our private serial structure */