sctp: delete free member from struct sctp_sched_ops

After commit 9ed7bfc7

 ("sctp: fix memory leak in
sctp_stream_outq_migrate()"), sctp_sched_set_sched() is the only
place calling sched->free(), and it can actually be replaced by
sched->free_sid() on each stream, and yet there's already a loop
to traverse all streams in sctp_sched_set_sched().

This patch adds a function sctp_sched_free_sched() where it calls
sched->free_sid() for each stream to replace sched->free() calls
in sctp_sched_set_sched() and then deletes the unused free member
from struct sctp_sched_ops.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://lore.kernel.org/r/e10aac150aca2686cb0bd0570299ec716da5a5c0.1669849471.git.lucien.xin@gmail.com


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