USB: lvtest: return proper error code in probe

lvs_rh_probe() can return some nonnegative value from usb_control_msg()
when it is less than "USB_DT_HUB_NONVAR_SIZE + 2" that is considered as
a failure. Make lvs_rh_probe() return -EINVAL in this case.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Evgeny Novikov <novikov@ispras.ru>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200805090643.3432-1-novikov@ispras.ruSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/lvstest.c

@@ -426,7 +426,7 @@ static int lvs_rh_probe(struct usb_interface *intf,
 			USB_DT_SS_HUB_SIZE, USB_CTRL_GET_TIMEOUT);
 	if (ret < (USB_DT_HUB_NONVAR_SIZE + 2)) {
 		dev_err(&hdev->dev, "wrong root hub descriptor read %d\n", ret);
-		return ret;
+		return ret < 0 ? ret : -EINVAL;
 	}
 
 	/* submit urb to poll interrupt endpoint */