scsi: ufs: ufs-mediatek: Fix power down spec violation

As per spec, e.g. JESD220E chapter 7.2, while powering off the UFS device,
RST_N signal should be between VSS(Ground) and VCCQ/VCCQ2. The power down
sequence after fixing:

Power down:

 1. Assert RST_N low

 2. Turn-off VCC

 3. Turn-off VCCQ/VCCQ2

Link: https://lore.kernel.org/r/1620813706-25331-1-git-send-email-peter.wang@mediatek.com
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufs-mediatek.c

@@ -922,6 +922,7 @@ static void ufs_mtk_vreg_set_lpm(struct ufs_hba *hba, bool lpm)
 static int ufs_mtk_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 {
 	int err;
+	struct arm_smccc_res res;
 
 	if (ufshcd_is_link_hibern8(hba)) {
 		err = ufs_mtk_link_set_lpm(hba);
@@ -941,6 +942,9 @@ static int ufs_mtk_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 			goto fail;
 	}
 
+	if (ufshcd_is_link_off(hba))
+		ufs_mtk_device_reset_ctrl(0, res);
+
 	return 0;
 fail:
 	/*