mceusb: fix NULL-deref at probe

commit 03eb2a557ed552e920a0942b774aaf931596eec1 upstream.

Make sure to check for the required out endpoint to avoid dereferencing
a NULL-pointer in mce_request_packet should a malicious device lack such
an endpoint. Note that this path is hit during probe.

Fixes: 66e89522 ("V4L/DVB: IR: add mceusb IR receiver driver")

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>