[SCTP]: #if 0 sctp_update_copy_cksum()

sctp_update_copy_cksum() is no longer used.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>