This macro was added but never used, remove it.

This is to fix the following warning when compiling the QAT driver
using the clang compiler with CC=clang W=2:
    drivers/crypto/intel/qat/qat_common/adf_cnv_dbgfs.c:19:9: warning: macro is not used [-Wunused-macros]
       19 | #define CNV_SLICE_ERR_MASK              GENMASK(7, 0)
          |         ^

Fixes: d807f024 ("crypto: qat - add cnv_errors debugfs file")
Signed-off-by: Adam Guerin <adam.guerin@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>