sctp: return back transport in __sctp_rcv_init_lookup

Prior to this patch, it used a local variable to save the transport that is
looked up by __sctp_lookup_association(), and didn't return it back. But in
sctp_rcv, it is used to initialize chunk->transport. So when hitting this,
even if it found the transport, it was still initializing chunk->transport
with null instead.

This patch is to return the transport back through transport pointer
that is from __sctp_rcv_lookup_harder().

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>