scsi: lpfc: nvmet: Avoid hang / use-after-free again when destroying targetport

scsi: lpfc: nvmet: Avoid hang / use-after-free again when destroying targetport

We cannot wait on a completion object in the lpfc_nvme_targetport structure
in the _destroy_targetport() code path because the NVMe/fc transport will
free that structure immediately after the .targetport_delete() callback.
This results in a use-after-free, and a crash if slub_debug=FZPU is
enabled.

An earlier fix put put the completion on the stack, but commit dc78a6026f24
("scsi: lpfc: Correct localport timeout duration error") subsequently
changed the code to reference the completion through a pointer in the
object rather than the local stack variable.  Fix this by using the stack
variable directly.

Link: https://lore.kernel.org/r/20200729231011.13240-1-emilne@redhat.com
Fixes: dc78a6026f24 ("scsi: lpfc: Correct localport timeout duration error")
Reviewed-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>