sctp: remove the left unnecessary check for chunk in sctp_renege_events

Commit fb234035 ("sctp: remove the useless check in
sctp_renege_events") forgot to remove another check for
chunk in sctp_renege_events.

Dan found this when doing a static check.

This patch is to remove that check, and also to merge
two checks into one 'if statement'.

Fixes: fb234035

 ("sctp: remove the useless check in sctp_renege_events")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>