ACPI: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 86c1059..449d86d 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -82,6 +82,7 @@ static int acpi_processor_errata_piix4(struct pci_dev *dev)
 		 * PIIX4 models.
 		 */
 		errata.piix4.throttle = 1;
+		/* fall through*/
 
 	case 2:		/* PIIX4E */
 	case 3:		/* PIIX4M */