sctp: Reduce switch/case indent

Make the case labels the same indent as the switch.

git diff -w shows useless break;s removed after returns
and a comment added to an unnecessary default: break;
because of a dubious gcc warning.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>