ACPI: SPCR: Mark expected switch fall-through in acpi_parse_spcr

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

Addresses-Coverity-ID: 1465078
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/spcr.c

@@ -115,6 +115,7 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
 			table->serial_port.access_width))) {
 		default:
 			pr_err("Unexpected SPCR Access Width.  Defaulting to byte size\n");
+			/* fall through */
 		case 8:
 			iotype = "mmio";
 			break;