net_sched: sch_sfq: annotate data-races around q->perturb_period

sfq_perturbation() reads q->perturb_period locklessly.
Add annotations to fix potential issues.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240430180015.3111398-1-edumazet@google.com


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