scsi: lpfc: Prevent use-after-free during rmmod with mapped NVMe rports

During rmmod, when dev_loss_tmo callback is called, an ndlp kref count is
decremented twice.  Once for SCSI transport registration and second to
remove the initial node allocation kref.  If there is also an NVMe
transport registration, another reference count decrement is expected in
lpfc_nvme_unregister_port().

Race conditions between the NVMe transport remoteport_delete and
dev_loss_tmo callbacks sometimes results in premature ndlp object release
resulting in use-after-free issues.

Fix by not dropping the ndlp object in dev_loss_tmo callback with an
outstanding NVMe transport registration.  Inversely, mark the final
NLP_DROPPED flag in lpfc_nvme_unregister_port when rmmod flag is set.

Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Link: https://lore.kernel.org/r/20230908211923.37603-1-justintee8345@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>