sctp: Correct spelling in headers

Correct spelling in sctp.h and structs.h.
As reported by codespell.

Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Simon Horman <horms@kernel.org>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/20240822-net-spell-v1-10-3a98971ce2d2@kernel.org


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