crypto: qat - remove unneeded variable

Remove unneeded variable val_indx.
Issue found by a static analyzer.

Reported-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>