crypto: qat - add cnv_errors debugfs file

The Compress and Verify (CnV) feature check and ensures data integrity
in the compression operation. The implementation of CnV keeps a record
of the CnV errors that have occurred since the driver was loaded.

Expose CnV error stats by providing the "cnv_errors" file under
debugfs. This includes the number of errors detected up to now and
the type of the last error. The error count is provided on a per
Acceleration Engine basis and it is reset every time the driver is loaded.

Signed-off-by: Lucas Segarra Fernandez <lucas.segarra.fernandez@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>