nvme-fc: use lock accessing port_state and rport state

nvme_fc_unregister_remote removes the remote port on a lport object at
any point in time when there is no active association. This races with
with the reconnect logic, because nvme_fc_create_association is not
taking a lock to check the port_state and atomically increase the
active count on the rport.

Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Closes: https://lore.kernel.org/all/u4ttvhnn7lark5w3sgrbuy2rxupcvosp4qmvj46nwzgeo5ausc@uyrkdls2muwx


Signed-off-by: Daniel Wagner <wagi@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>