Merge the functionality mostly into amdgpu_vm_bo_update_mapping.
This way we can even handle small contiguous system pages without
to much extra CPU overhead.
v2: fix typo, keep the cursor as it is for now
Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-by: Madhav Chauhan <madhav.chauhan@amd.com> (v1) Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>