sctp: Fix regression introduced by new sctp_connectx api

A new (unrealeased to the user) sctp_connectx api

c6ba68a26645dbc5029a9faa5687ebe6fcfc53e4
    sctp: support non-blocking version of the new sctp_connectx() API

introduced a regression cought by the user regression test
suite.  In particular, the API requires the user library to
re-allocate the buffer and could potentially trigger a SIGFAULT.

This change corrects that regression by passing the original
address buffer to the kernel unmodified, but still allows for
a returned association id.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>