usb: host: 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/latest/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-throughSigned-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200707195023.GA3792@embeddedorSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-dbg.c

@@ -823,7 +823,7 @@ static ssize_t fill_registers_buffer(struct debug_buffer *buf)
 				break;
 			case 0:		/* illegal reserved capability */
 				cap = 0;
-				/* FALLTHROUGH */
+				fallthrough;
 			default:		/* unknown */
 				break;
 			}

drivers/usb/host/ehci-fsl.c

@@ -234,7 +234,7 @@ static int ehci_fsl_setup_phy(struct usb_hcd *hcd,
 		break;
 	case FSL_USB2_PHY_UTMI_WIDE:
 		portsc |= PORT_PTS_PTW;
-		/* fall through */
+		fallthrough;
 	case FSL_USB2_PHY_UTMI:
 		/* Presence of this node "has_fsl_erratum_a006918"
 		 * in device-tree is used to stop USB controller
@@ -244,7 +244,7 @@ static int ehci_fsl_setup_phy(struct usb_hcd *hcd,
 			dev_warn(dev, "USB PHY clock invalid\n");
 			return -EINVAL;
 		}
-		/* fall through */
+		fallthrough;
 	case FSL_USB2_PHY_UTMI_DUAL:
 		/* PHY_CLK_VALID bit is de-featured from all controller
 		 * versions below 2.4 and is to be checked only for

drivers/usb/host/ehci-hcd.c

@@ -982,7 +982,7 @@ ehci_endpoint_disable (struct usb_hcd *hcd, struct usb_host_endpoint *ep)
 			start_unlink_async(ehci, qh);
 		else
 			start_unlink_intr(ehci, qh);
-		/* FALL THROUGH */
+		fallthrough;
 	case QH_STATE_COMPLETING:	/* already in unlinking */
 	case QH_STATE_UNLINK:		/* wait for hw to finish? */
 	case QH_STATE_UNLINK_WAIT:
@@ -999,7 +999,7 @@ ehci_endpoint_disable (struct usb_hcd *hcd, struct usb_host_endpoint *ep)
 			qh_destroy(ehci, qh);
 			break;
 		}
-		/* fall through */
+		fallthrough;
 	default:
 		/* caller was supposed to have unlinked any requests;
 		 * that's not our job.  just leak this memory.

drivers/usb/host/ehci-q.c

@@ -874,7 +874,7 @@ qh_make (
 	switch (urb->dev->speed) {
 	case USB_SPEED_LOW:
 		info1 |= QH_LOW_SPEED;
-		/* FALL THROUGH */
+		fallthrough;
 
 	case USB_SPEED_FULL:
 		/* EPS 0 means "full" */

drivers/usb/host/ehci-sched.c

@@ -2475,7 +2475,7 @@ static void scan_isoc(struct ehci_hcd *ehci)
 			ehci_dbg(ehci, "corrupt type %d frame %d shadow %p\n",
 					type, frame, q.ptr);
 			/* BUG(); */
-			/* FALL THROUGH */
+			fallthrough;
 		case Q_TYPE_QH:
 		case Q_TYPE_FSTN:
 			/* End of the iTDs and siTDs */