sctp: Unwind address notifier registration on failure

sctp: Unwind address notifier registration on failure

sctp_v4_add_protocol() and sctp_v6_add_protocol() register their
address notifiers before registering the SCTP protocol handlers. If
protocol registration fails, the functions return without unregistering
the notifiers.

Unregister the notifiers on the protocol registration failure paths.
Also propagate notifier registration failures instead of ignoring them.

Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
Link: https://patch.msgid.link/20260608162230.46644-1-dbgh9129@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>