scsi: hisi_sas: Flush workqueue in hisi_sas_v3_remove()

If the controller reset occurs at the same time as driver removal, it may
be possible that the interrupts have been released prior to the host
softreset, and calling pci_irq_vector() there causes a WARN:

WARNING: CPU: 37 PID: 1542 /pci/msi.c:1275 pci_irq_vector+0xc0/0xd0
Call trace:
pci_irq_vector+0xc0/0xd0
disable_host_v3_hw+0x58/0x5b0 [hisi_sas_v3_hw]
soft_reset_v3_hw+0x40/0xc0 [hisi_sas_v3_hw]
hisi_sas_controller_reset+0x150/0x260 [hisi_sas_main]
hisi_sas_rst_work_handler+0x3c/0x58 [hisi_sas_main]

To fix, flush the driver workqueue prior to releasing the interrupts to
ensure any resets have been completed.

Link: https://lore.kernel.org/r/1611659068-131975-5-git-send-email-john.garry@huawei.comSigned-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hisi_sas/hisi_sas_v3_hw.c

@@ -4572,6 +4572,7 @@ static void hisi_sas_v3_remove(struct pci_dev *pdev)
 		del_timer(&hisi_hba->timer);
 
 	sas_unregister_ha(sha);
+	flush_workqueue(hisi_hba->wq);
 	sas_remove_host(sha->core.shost);
 
 	hisi_sas_v3_destroy_irqs(pdev, hisi_hba);