Correct unused parameter warnings in io algorithms

[robertmaynard]

Starting in CUDA 11.3, nvcc will start to unconditionally warn about unused parameters on functions/methods that are in anonymous namespaces.

[codecov]

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##             branch-21.08    #8480   +/-   ##
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  Files                   ?      109           
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  Hits                    ?    14847           
  Misses                  ?     3073           
  Partials                ?        0           

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[robertmaynard]

@gpucibot merge