Merge branch '2023-08-25-add-persistent-config-editor-via-expo' into next

To quote the author:
So far cedit does not support reading and writing the configuration.
This series add several features related to this:

First, it adds support for using a file on a filesystem. This is in
FDT format and provides enough information to reset the cedit back to
the saved settings.

Second, it adds support for using the U-Boot environment. Since the
environment is generally saved across reboots, this feature provides an
easy way of storing the state on most boards. The variables all have a
'c.' prefix to avoid confusion with other variables.

Finally it adds support for using CMOS RAM. This is commonly used on x86
devices to store BIOS settings. The expo schema provides information on
the register layout.

Some other minor tweaks and improvements are included along the way.