sg_io: print names of array fields and corresponding length fields

sg_io: print names of array fields and corresponding length fields

* sg_io_v3.c (decode_request): Print names of cmd_len, cmdp,
and dxferp fields.
(decode_response): Print names of dxferp, sb_len_wr, and sbp fields.
* sg_io_v4.c (decode_request): Print names of request_len, request,
dout_xfer_len, and dout_xferp fields.
(decode_response): Print names of response_len, response,
and din_xferp fields.