unbreak compilation of the benchmark, allow benchmarking specific bit depths
unbreak compilation of the benchmark, allow benchmarking specific bit depths

maciekcc/gemmlowp,dave-andersen/gemmlowp,dave-andersen/gemmlowp,maciekcc/gemmlowp,petewarden/gemmlowp,efeguney/gemmlowp,google/gemmlowp,google/gemmlowp,google/gemmlowp,miaowang14/gemmlowp,miaowang14/gemmlowp,efeguney/gemmlowp,petewarden/gemmlowp,miaowang14/gemmlowp,efeguney/gemmlowp,petewarden/gemmlowp,petewarden/gemmlowp,google/gemmlowp,maciekcc/gemmlowp,dave-andersen/gemmlowp