The it8801 template is helpful but in the current state it does not
allow changing the device address as that is in the template itself. Fix
that by moving the template content down a level in the hierarchy, so
that it extends the mfd device itself rather than than instantiate it,
then the base instance can have any address, now the only limitation is
that only one instance is possible, but that is probably alright for
now.
Alternatives would be to use a define for the address, or even a
template per address, but this feels like a better compromise for now.
This may also use
https://github.com/zephyrproject-rtos/zephyr/pull/82825 in the future if
that ever becomes a thing.
Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
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