fix grouped bwd example host issue

example/32_batched_gemm_scale_softmax_gemm/grouped_multihead_attention_backward.cpp

@@ -948,9 +948,12 @@ int run(int argc, char* argv[])
                 {
                     auto idx_gmo = idx_gmn;
                     idx_gmo[2]   = o;
-                    ygrad_dot_y += ygrad_g_m_o(idx_gmo) * y_g_m_os[i](idx_gmo);
+                    ygrad_dot_y += ck::type_convert<AccDataType>(ygrad_g_m_o(idx_gmo)) *
+                                   ck::type_convert<AccDataType>(y_g_m_os[i](idx_gmo));
                 }
-                self(idx_gmn) = p_g_m_ns[i](idx_gmn) * (pgrad_g_m_n(idx_gmn) - ygrad_dot_y);
+                self(idx_gmn) = ck::type_convert<DataType>(
+                    ck::type_convert<AccDataType>(p_g_m_ns[i](idx_gmn)) *
+                    (ck::type_convert<AccDataType>(pgrad_g_m_n(idx_gmn)) - ygrad_dot_y));
             });
 
             auto p_drop_g_n_m = p_drop_g_m_ns[i].Transpose({0, 2, 1});