mfd: Add ACPI support to Kontron PLD driver

Recent Kontron COMe modules identify the PLD device using the hardware
id KEM0001 in the ACPI table.
This patch adds support for probing the device using the HID and also
retrieving the resources.

As this is not available for all products, the DMI based detection still
needs to be around for older systems. It is executed if no matching ACPI
HID is found during registering the platform driver or no specific
device id is forced.
If a device is detected using ACPI and no resource information is
available, the default io resource is used.

Forcing a device id with the force_device_id parameter and therefore
manually generating a platform device takes precedence over ACPI during
probing.

Signed-off-by: Michael Brunner <michael.brunner@kontron.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>