scsi: lpfc: resolve static checker warning in lpfc_sli4_hba_unset

The patch that replaced io channels for hdw_queues now reports the
following static checker warning:

drivers/scsi/lpfc/lpfc_init.c:11136 lpfc_sli4_hba_unset()
 error: we previously assumed 'phba->pport' could be null (see line 11074)

Resolve by adding a pport NULL check.

[mkp: tag tweak]

Fixes: cdb42bec

 ("scsi: lpfc: Replace io_channels for nvme and fcp with general hdw_queues per cpu"_
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>