crypto: cavium - prevent integer overflow loading firmware

The "code_length" value comes from the firmware file.  If your firmware
is untrusted realistically there is probably very little you can do to
protect yourself.  Still we try to limit the damage as much as possible.
Also Smatch marks any data read from the filesystem as untrusted and
prints warnings if it not capped correctly.

The "ntohl(ucode->code_length) * 2" multiplication can have an
integer overflow.

Fixes: 9e2c7d99

 ("crypto: cavium - Add Support for Octeon-tx CPT Engine")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>