Fixes function signatures for torch::nn::Functional (#2463)

torchvision/csrc/models/modelsimpl.h

@@ -14,22 +14,22 @@ namespace modelsimpl {
 // TODO here torch::relu_ and torch::adaptive_avg_pool2d wrapped in
 // torch::nn::Fuctional don't work. so keeping these for now
 
-inline torch::Tensor& relu_(torch::Tensor x) {
-  return torch::relu_(x);
+inline torch::Tensor& relu_(const torch::Tensor& x) {
+  return x.relu_();
 }
 
-inline torch::Tensor relu6_(torch::Tensor x) {
+inline torch::Tensor& relu6_(const torch::Tensor& x) {
   return x.clamp_(0, 6);
 }
 
 inline torch::Tensor adaptive_avg_pool2d(
-    torch::Tensor x,
+    const torch::Tensor& x,
     torch::ExpandingArray<2> output_size) {
   return torch::adaptive_avg_pool2d(x, output_size);
 }
 
 inline torch::Tensor max_pool2d(
-    torch::Tensor x,
+    const torch::Tensor& x,
     torch::ExpandingArray<2> kernel_size,
     torch::ExpandingArray<2> stride) {
   return torch::max_pool2d(x, kernel_size, stride);