USB: uss720: fix NULL-deref at probe

commit f259ca3eed6e4b79ac3d5c5c9fb259fb46e86217 upstream.

Make sure to check the number of endpoints to avoid dereferencing a
NULL-pointer or accessing memory beyond the endpoint array should a
malicious device lack the expected endpoints.

Note that the endpoint access that causes the NULL-deref is currently
only used for debugging purposes during probe so the oops only happens
when dynamic debugging is enabled. This means the driver could be
rewritten to continue to accept device with only two endpoints, should
such devices exist.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Corey Edwards <ensabahnur16@gmail.com>