scsi: lpfc: Fix a possible data race in lpfc_unregister_fcf_rescan()

The variable phba->fcf.fcf_flag is often protected by the lock
phba->hbalock() when is accessed. Here is an example in
lpfc_unregister_fcf_rescan():

  spin_lock_irq(&phba->hbalock);
  phba->fcf.fcf_flag |= FCF_INIT_DISC;
  spin_unlock_irq(&phba->hbalock);

However, in the same function, phba->fcf.fcf_flag is assigned with 0
without holding the lock, and thus can cause a data race:

  phba->fcf.fcf_flag = 0;

To fix this possible data race, a lock and unlock pair is added when
accessing the variable phba->fcf.fcf_flag.

Reported-by: BassCheck <[email protected]>
Signed-off-by: Tuo Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Justin Tee <[email protected]>
Reviewed-by: Laurence Oberman <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

Author: lituo1996

drivers/scsi/lpfc/lpfc_hbadisc.c

@@ -6944,7 +6944,9 @@ lpfc_unregister_fcf_rescan(struct lpfc_hba *phba)
 	if (rc)
 		return;
 	/* Reset HBA FCF states after successful unregister FCF */
+	spin_lock_irq(&phba->hbalock);
 	phba->fcf.fcf_flag = 0;
+	spin_unlock_irq(&phba->hbalock);
 	phba->fcf.current_rec.flag = 0;
 
 	/*