client/server: convert ss_data to use an offset instead of fixed position

client/server: convert ss_data to use an offset instead of fixed position

Store the location of the ss_data in the payload itself, rather than
assuming that it is always located at a fixed location, directly after
the cmd_ts_pdu data.

This is done as a cleanup patch in order to be able to handle
clat_prio_stats, which just like ss_data, may or may not be part of the
payload.

Server version is intentionally not incremented, as it will be incremented
in a later patch in the series. No need to bump it multiple times for the
same patch series.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20220203192814.18552-5-Niklas.Cassel@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>