ACPI: sbshc: Fix fall-through warning for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a
fallthrough warning by simply dropping the empty default case at
the bottom.

This contributes to the ongoing efforts to globally enable
-Wimplicit-fallthrough for Clang.

Link: https://github.com/KSPP/linux/issues/115
Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/lkml/CAJZ5v0hLYWKX__oZdcCY0D20pNqpw8SkiTPOCNOtpqe--QLp4Q@mail.gmail.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/sbshc.c

@@ -231,7 +231,6 @@ static int smbus_alarm(void *context)
 		case ACPI_SBS_BATTERY:
 			acpi_os_execute(OSL_NOTIFY_HANDLER,
 					acpi_smbus_callback, hc);
-		default:;
 	}
 	mutex_unlock(&hc->lock);
 	return 0;