USB: lvtest: fix NULL-deref at probe

Make sure to check the number of endpoints to avoid dereferencing a
NULL-pointer should the probed device lack endpoints.

Note that this driver does not bind to any devices by default.

Fixes: ce21bfe603 ("USB: Add LVS Test device driver")
Cc: stable <stable@vger.kernel.org>     # 3.17
Cc: Pratyush Anand <pratyush.anand@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/lvstest.c

@@ -366,6 +366,10 @@ static int lvs_rh_probe(struct usb_interface *intf,
 
 	hdev = interface_to_usbdev(intf);
 	desc = intf->cur_altsetting;
+
+	if (desc->desc.bNumEndpoints < 1)
+		return -ENODEV;
+
 	endpoint = &desc->endpoint[0].desc;
 
 	/* valid only for SS root hub */