benchdnn: fixup bf16 pool

- workaround to avoid cvt on non-avx512_core

Author: shelleygoel

tests/benchdnn/pool/cfg.cpp

@@ -56,15 +56,16 @@ const _dt_conf_t conf_f16 = {
     {mkldnn_f16, -flt16_max, flt16_max, -32, 32, 1e-3},
 };
 
-const bfloat16_t bflt16_max = mkldnn::impl::nstl::numeric_limits<bfloat16_t>::max();
+#define BFLT16_MAX 3.38953138925153547590470800371487866880e+38F
 const _dt_conf_t conf_bf16 = {
     /* Although integers are expected, eps is needed to cover
      * for the division error */
-    {mkldnn_bf16, -bflt16_max, bflt16_max, -32, 32, 1e-2},
+    {mkldnn_bf16, -BFLT16_MAX, BFLT16_MAX, -32, 32, 1e-2},
     {},
     {},
-    {mkldnn_bf16, -bflt16_max, bflt16_max, -32, 32, 5e-2},
+    {mkldnn_bf16, -BFLT16_MAX, BFLT16_MAX, -32, 32, 5e-2},
 };
+#undef BFLT16_MAX
 
 const _dt_conf_t conf_s8 = {
     {mkldnn_s8,  INT8_MIN,  INT8_MAX, INT8_MIN,  INT8_MAX, 0.},