sctp: fix transport encap_port update in sctp_vtag_verify

transport encap_port update should be updated when sctp_vtag_verify()
succeeds, namely, returns 1, not returns 0. Correct it in this patch.

While at it, also fix the indentation.

Fixes: a1dd2cf2 ("sctp: allow changing transport encap_port by peer packets")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>