sctp: Move the percpu sockets counter out of sctp_proc_init

The percpu sctp socket counter has nothing at all to do with the sctp
proc files, and having it in the wrong initialization is confusing,
and makes network namespace support a pain.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>