[SCTP]: Audit return code of create_proc_*

From: Christophe Lucas <clucas@rotomalug.org>

Audit return of create_proc_* functions.

Signed-off-by: Christophe Lucas <clucas@rotomalug.org>
Signed-off-by: Domen Puncer <domen@coderock.org>
Signed-off-by: David S. Miller <davem@davemloft.net>