fix scale type in alpha and beta (#48887)

paddle/fluid/operators/fused/fused_multi_transformer_op.cu.h

@@ -1530,21 +1530,16 @@ class CublasFusedMLP {
          beta16 =
              add_residual ? static_cast<half>(1.0) : static_cast<half>(0.0);
 
-    void *alpha = nullptr, *beta = nullptr;
+    void *alpha = &alpha32, *beta = &beta32;
     if (std::is_same<T, double>::value) {
       alpha = &alpha64;
       beta = &beta64;
-    } else if (std::is_same<T, float>::value) {
-      alpha = &alpha64;
-      beta = &beta64;
-    } else if (std::is_same<T, phi::dtype::float16>::value) {
+    }
+
+    if (std::is_same<T, phi::dtype::float16>::value &&
+        FLAGS_gemm_use_half_precision_compute_type) {
       alpha = &alpha16;
       beta = &beta16;
-    } else {
-      PADDLE_ENFORCE_EQ(true,
-                        false,
-                        platform::errors::InvalidArgument(
-                            "Only support double, float, half data type. "));
     }
 
     const auto *x_data = x->data<T>();