ACPI / scan: Rename acpi_is_serial_bus_slave() for more general use

Currently the ACPI scan has special handling for serial bus slaves, in that
it makes it the responsibility of the slave device's parent to enumerate
the device.

To support other types of slave devices which require the same special
handling but where the bus is not strictly a serial bus, such as devices on
the HiSilicon LPC controller bus, rename acpi_is_serial_bus_slave() to
acpi_device_enumeration_by_parent(), so that the name can fit the wider
purpose.

Also rename the associated device flag acpi_device_flags.serial_bus_slave
to .enumeration_by_parent.

Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>