asmc_key_dump() branched on the backend, but asmc_key_dump_by_index()
already dispatches on it, so the PIO arm open-coded a transaction it could
have called. Keep one printer for both.
Output is unchanged. The PIO arm checked asmc_key_read()'s return value
instead of printing a zeroed buffer; the merged printer keeps that. Its
retry exhaustion message is gone, which asmc_dumpall() cannot observe.