[PHI] Add multinomial output defs (#51357)

* add multinomial output defs

* fix register on gpu

paddle/fluid/framework/new_executor/interpreter/interpreter_util.cc

@@ -70,7 +70,6 @@ static std::set<std::string> OpsNeedSetOutputDtypeWhenRegisterPhiKernel = {
     "merged_adam",
     "momentum",
     "multiclass_nms3",
-    "multinomial",
     "nanmedian",
     "sync_batch_norm_grad",
     "unique",

paddle/phi/kernels/cpu/multinomial_kernel.cc

@@ -45,4 +45,6 @@ void MultinomialKernel(const Context& dev_ctx,
 }  // namespace phi
 
 PD_REGISTER_KERNEL(
-    multinomial, CPU, ALL_LAYOUT, phi::MultinomialKernel, float, double) {}
+    multinomial, CPU, ALL_LAYOUT, phi::MultinomialKernel, float, double) {
+  kernel->OutputAt(0).SetDataType(phi::DataType::INT64);
+}

paddle/phi/kernels/gpu/multinomial_kernel.cu

@@ -296,6 +296,8 @@ PD_REGISTER_KERNEL(multinomial,  // cuda_only
                    ALL_LAYOUT,
                    phi::MultinomialKernel,
                    float,
-                   double) {}
+                   double) {
+  kernel->OutputAt(0).SetDataType(phi::DataType::INT64);
+}
 
 #endif