crypto: qat - remove unused function

Remove unused function qat_dh_get_params().
This is to fix the following warning when compiling the driver with
CC=clang W=1

    drivers/crypto/qat/qat_common/qat_asym_algs.c:207:34: warning: unused function 'qat_dh_get_params' [-Wunused-function]

Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Fiona Trahe <fiona.trahe@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>