UPSTREAM: USB: mct_u232: add sanity checking in probe

commit 4e9a0b05 upstream.

An attack using the lack of sanity checking in probe is known. This
patch checks for the existence of a second port.

CVE-2016-3136
BUG: 28242610
Signed-off-by: Oliver Neukum <ONeukum@suse.com>
[johan: add error message ]
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
Change-Id: I284ad648c2087c34a098d67e0cc6d948a568413c