ACPI: platform: Unregister stale platform devices

When commit 68bdb677 ("ACPI: add support for ACPI reconfiguration
notifiers") introduced reconfiguration notifiers, it missed the point
that the ACPI table, which might be loaded and then unloaded via
ConfigFS, could contain devices that were not enumerated by their
parents.

In such cases, the stale platform device is dangling in the system
while the rest of the devices from the same table are already gone.

Introduce acpi_platform_device_remove_notify() notifier that, in
similar way to I²C or SPI buses, unregisters the platform devices
on table removal event.

Fixes: 68bdb677 ("ACPI: add support for ACPI reconfiguration notifiers")
Depends-on: 00500147

 ("drivers: Introduce device lookup variants by ACPI_COMPANION device")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[ rjw: Changelog & function rename ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>