stat: simplify add_lat_percentile_prio_sample()

stat: simplify add_lat_percentile_prio_sample()

add_lat_percentile_prio_sample() currently adds both a per priority sample
and a regular sample.

Since these two samples are completely unrelated, it is very confusing that
the add_lat_percentile_prio_sample() also adds a regular sample.

Remove the add_lat_percentile_sample() function call from
add_lat_percentile_prio_sample(), and let functions calling
add_lat_percentile_prio_sample() call add_lat_percentile_sample()
explicitly. This makes the flow in e.g. add_clat_sample() much easier to
follow.

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/20211125132020.109955-6-Niklas.Cassel@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>