PCI: imx6: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Link: https://lore.kernel.org/r/20200722031903.GA3711@embeddedorSigned-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/pci/controller/dwc/pci-imx6.c

@@ -439,7 +439,7 @@ static int imx6_pcie_enable_ref_clk(struct imx6_pcie *imx6_pcie)
 		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
 				   IMX6SX_GPR12_PCIE_TEST_POWERDOWN, 0);
 		break;
-	case IMX6QP:		/* FALLTHROUGH */
+	case IMX6QP:
 	case IMX6Q:
 		/* power up core phy and enable ref clock */
 		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
@@ -642,7 +642,7 @@ static void imx6_pcie_init_phy(struct imx6_pcie *imx6_pcie)
 		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
 				   IMX6SX_GPR12_PCIE_RX_EQ_MASK,
 				   IMX6SX_GPR12_PCIE_RX_EQ_2);
-		/* FALLTHROUGH */
+		fallthrough;
 	default:
 		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
 				   IMX6Q_GPR12_PCIE_CTL_2, 0 << 10);
@@ -1105,7 +1105,7 @@ static int imx6_pcie_probe(struct platform_device *pdev)
 			dev_err(dev, "pcie_aux clock source missing or invalid\n");
 			return PTR_ERR(imx6_pcie->pcie_aux);
 		}
-		/* fall through */
+		fallthrough;
 	case IMX7D:
 		if (dbi_base->start == IMX8MQ_PCIE2_BASE_ADDR)
 			imx6_pcie->controller_id = 1;