tests: benchdnn: matmul: ensure mx scale value within range

Author: kealan-barbieri

tests/benchdnn/matmul/ref_matmul.cpp

@@ -234,7 +234,8 @@ void compute_ref_matmul(const prb_t *prb, const args_t &args) {
                     }
                     dst_scale = round_to_nearest_representable(
                                         dst_scale_dt, dst_scale)
-                            / max_dt(prb->dst_dt());
+                            / round_to_nearest_representable(
+                                    dst_scale_dt, max_dt(prb->dst_dt()));
                     const auto dst_off = dst_off_f(
                             prb, mb, mc * dst_M_group, nc * dst_N_group);
                     const auto dscale_idx = dst_m.get_idx(dst_off,