Add a command to read edit settings from CMOS RAM, using the cedit
definition to indicate which registers and bits are used.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a command to write cedit settings to CMOS RAM so that it can be
preserved across a reboot. This uses a simple bit-encoding, where each
field has a 'bit position' and a 'bit length' in the schema.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a command to read cedit settings from environment variables so that
they can be restored as part of the environment.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a command to write cedit settings to environment variables so that
they can be stored with 'saveenv'.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a command to read cedit settings from a devicetree file.

Signed-off-by: Simon Glass <sjg@chromium.org>

Support writing settings from an expo into a file in FDT format. It
consists of a single node with a two properties for each sceneitem,
one with tag ID chosen by the user and another for its text value.

Signed-off-by: Simon Glass <sjg@chromium.org>

Split out the code which prepares the cedit for use, so we can call it
from a test.

Add a log category while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>

Before adding more functions to this interface, create a new header for
the configuration editor.

Fix up the expo header guard while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>