drm/amdgpu: Simplify AQL queue mapping

Do AQL queue double-mapping with a single attach call. That will make it
easier to create per-GPU BOs later, to be shared between the two BO VA
mappings on the same GPU.

Freeing the attachments is not necessary if map_to_gpu fails. These will be
cleaned up when the kdg_mem object is destroyed in
amdgpu_amdkfd_gpuvm_free_memory_of_gpu.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Oak Zeng <Oak.Zeng@amd.com>
Acked-by: Ramesh Errabolu <Ramesh.Errabolu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>