[CUDA] Backward convolution (#2431)

mlx/backend/common/utils.h

@@ -196,6 +196,9 @@ void shared_buffer_reshape(
     const Strides& out_strides,
     array& out);
 
+// Like the swapaxes op but safe to call in eval_gpu.
+array swapaxes_in_eval(const array& x, int axis1, int axis2);
+
 template <typename T>
 inline std::vector<T> remove_index(std::vector<T> vec, size_t index) {
   vec.erase(std::next(vec.begin(), index));