crypto: qat - do not shadow error code

Do not shadow the return code from adf_dev_down() in the error path of
the DEV_DOWN command.

Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Adam Guerin <adam.guerin@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>