Add a platform device tree passthrough for device properties. First,
the device's properties dictionary is consulted, and if it doesn't have
what we're looking for, we go ask the platform device tree. The upshot
is that we can g/c (or not have to add) code that duplicates values from
the device tree into the properties dictionary (either in something like
device_register() or in a driver attachment front-end -- there are multiple
example of both in the system, currently), and everyone gets to use a
consistent interface (which will, over time, allow more code to de-duplicated).

Implement back-ends for ACPI, Sun OpenBoot, and OpenFirmware (including FDT).

Add a device_register() hook for the platform device tree. For ACPI and
OpenFirmware (including FDT), use this to record the firmware path to
the device in the "device-path" property.

Introduce a device call "device-is-system-todr", which allows the
platform device tree to be consulted if there are multiple TODR / RTC
devices present on the system; if the call is not supported, the behavior
is un-changed: the first TODR device is attached, all others ignored. If
the call is supported, devices other than the specified system TODR are
skipped.

Implement this device call for FDT.

kern/59630

Device call interface definition files for the "device" and "pci"
subsystems.