fix align_up namespace in aligned_resource_adaptor.hpp (#820)

Fixes #819

Authors:
  - Rong Ou (https://github.com/rongou)

Approvers:
  - Mark Harris (https://github.com/harrism)
  - Conor Hoekstra (https://github.com/codereport)

URL: #820

include/rmm/mr/device/aligned_resource_adaptor.hpp

@@ -209,7 +209,7 @@ class aligned_resource_adaptor final : public device_memory_resource {
    */
   std::size_t upstream_allocation_size(std::size_t bytes) const
   {
-    auto const aligned_size = detail::align_up(bytes, allocation_alignment_);
+    auto const aligned_size = rmm::detail::align_up(bytes, allocation_alignment_);
     return aligned_size + allocation_alignment_ - rmm::detail::CUDA_ALLOCATION_ALIGNMENT;
   }