PCI/switchtec: Update the way of getting management VEP instance ID

Gen4 firmware adds DMA VEP and NVMe VEP support in VEP (virtual EP)
instance ID register in addtion to management EP, update the way of
getting management VEP instance ID.

Link: https://lore.kernel.org/r/20211014141859.11444-4-kelvin.cao@microchip.comSigned-off-by: Kelvin Cao <kelvin.cao@microchip.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/switch/switchtec.c

@@ -1133,7 +1133,7 @@ static int ioctl_pff_to_port(struct switchtec_dev *stdev,
 			break;
 		}
 
-		reg = ioread32(&pcfg->vep_pff_inst_id);
+		reg = ioread32(&pcfg->vep_pff_inst_id) & 0xFF;
 		if (reg == p.pff) {
 			p.port = SWITCHTEC_IOCTL_PFF_VEP;
 			break;
@@ -1179,7 +1179,7 @@ static int ioctl_port_to_pff(struct switchtec_dev *stdev,
 		p.pff = ioread32(&pcfg->usp_pff_inst_id);
 		break;
 	case SWITCHTEC_IOCTL_PFF_VEP:
-		p.pff = ioread32(&pcfg->vep_pff_inst_id);
+		p.pff = ioread32(&pcfg->vep_pff_inst_id) & 0xFF;
 		break;
 	default:
 		if (p.port > ARRAY_SIZE(pcfg->dsp_pff_inst_id))
@@ -1553,7 +1553,7 @@ static void init_pff(struct switchtec_dev *stdev)
 	if (reg < stdev->pff_csr_count)
 		stdev->pff_local[reg] = 1;
 
-	reg = ioread32(&pcfg->vep_pff_inst_id);
+	reg = ioread32(&pcfg->vep_pff_inst_id) & 0xFF;
 	if (reg < stdev->pff_csr_count)
 		stdev->pff_local[reg] = 1;