[SCTP]: sctp_process_init() and sctp_source() switched to net-endian.

both are done in one go since almost always we have result of
the latter immediately passed to the former.  Possibly non-obvious
note: sctp_process_param() is endian-agnostic

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>