treewide: 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

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index b1cd4d9..1a82058 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -190,7 +190,7 @@ struct ata_link *ata_link_next(struct ata_link *link, struct ata_port *ap,
 		case ATA_LITER_PMP_FIRST:
 			if (sata_pmp_attached(ap))
 				return ap->pmp_link;
-			/* fall through */
+			fallthrough;
 		case ATA_LITER_HOST_FIRST:
 			return &ap->link;
 		}
@@ -201,11 +201,11 @@ struct ata_link *ata_link_next(struct ata_link *link, struct ata_port *ap,
 		case ATA_LITER_HOST_FIRST:
 			if (sata_pmp_attached(ap))
 				return ap->pmp_link;
-			/* fall through */
+			fallthrough;
 		case ATA_LITER_PMP_FIRST:
 			if (unlikely(ap->slave_link))
 				return ap->slave_link;
-			/* fall through */
+			fallthrough;
 		case ATA_LITER_EDGE:
 			return NULL;
 		}
@@ -523,7 +523,7 @@ int atapi_cmd_type(u8 opcode)
 	case ATA_12:
 		if (atapi_passthru16)
 			return ATAPI_PASS_THRU;
-		/* fall thru */
+		fallthrough;
 	default:
 		return ATAPI_MISC;
 	}
@@ -1800,7 +1800,7 @@ int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class,
 	switch (class) {
 	case ATA_DEV_SEMB:
 		class = ATA_DEV_ATA;	/* some hard drives report SEMB sig */
-		/* fall through */
+		fallthrough;
 	case ATA_DEV_ATA:
 	case ATA_DEV_ZAC:
 		tf.command = ATA_CMD_ID_ATA;
@@ -2907,7 +2907,7 @@ int ata_bus_probe(struct ata_port *ap)
 	case -ENODEV:
 		/* give it just one more chance */
 		tries[dev->devno] = min(tries[dev->devno], 1);
-		/* fall through */
+		fallthrough;
 	case -EIO:
 		if (tries[dev->devno] == 1) {
 			/* This is the last chance, better to slow
@@ -3158,7 +3158,7 @@ int ata_down_xfermask_limit(struct ata_device *dev, unsigned int sel)
 
 	case ATA_DNXFER_FORCE_PIO0:
 		pio_mask &= 1;
-		/* fall through */
+		fallthrough;
 	case ATA_DNXFER_FORCE_PIO:
 		mwdma_mask = 0;
 		udma_mask = 0;
@@ -4694,7 +4694,7 @@ void ata_qc_complete(struct ata_queued_cmd *qc)
 			    qc->tf.feature != SETFEATURES_RA_ON &&
 			    qc->tf.feature != SETFEATURES_RA_OFF)
 				break;
-			/* fall through */
+			fallthrough;
 		case ATA_CMD_INIT_DEV_PARAMS: /* CHS translation changed */
 		case ATA_CMD_SET_MULTI: /* multi_count changed */
 			/* revalidate device */