sctp: reset probe_timer in sctp_transport_pl_update

sctp: reset probe_timer in sctp_transport_pl_update

[ Upstream commit c6ea04ea692fa0d8e7faeb133fcd28e3acf470a0 ]

sctp_transport_pl_update() is called when transport update its dst and
pathmtu, instead of stopping the PLPMTUD probe timer, PLPMTUD should
start over and reset the probe timer. Otherwise, the PLPMTUD service
would stop.

Fixes: 92548ec2f1f9 ("sctp: add the probe timer in transport for PLPMTUD")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>