net: qstat: extend kdoc about get_base_stats

mlx5 has a dedicated queue for PTP packets. Clarify that
this sort of queues can also be accounted towards the base.

Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://lore.kernel.org/r/20240529162922.3690698-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>