[SCSI] lpfc 8.1.7: Add lpfc_sli_flush_mbox_queue() function

Add lpfc_sli_flush_mbox_queue() function and use it in lpfc_offline() call
to avoid deadlock on thread block.

Signed-off-by: James Smart <James.Smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/lpfc/lpfc_init.c b/drivers/scsi/lpfc/lpfc_init.c
index 2a81df0..ee591c1 100644
--- a/drivers/scsi/lpfc/lpfc_init.c
+++ b/drivers/scsi/lpfc/lpfc_init.c
@@ -1353,6 +1353,7 @@
 	psli = &phba->sli;
 
 	lpfc_linkdown(phba);
+	lpfc_sli_flush_mbox_queue(phba);
 
 	for (i = 0; i < psli->num_rings; i++) {
 		pring = &psli->ring[i];