sctp: make array sctp_sched_ops static

The array sctp_sched_ops  is local to the source and
does not need to be in global scope, so make it static.

Cleans up sparse warning:
symbol 'sctp_sched_ops' was not declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>