sctp: Do not enable peer IPv6 address support on PF_INET socket

If socket is create by PF_INET type, it can not used IPv6 address to
send/recv DATA, So we can not used IPv6 address even if peer tell us it
support IPv6 address.
This patch fix to only enabled peer IPv6 address support on PF_INET6 socket.

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