regulator: dt-bindings: maxim,max8997: convert to dtschema

Convert the Maxim MAX8997 PMIC bindings to DT schema format.  Extend the
examples with additional one copied from kernel's exynos4210-origen.dts.
Also the binding descriptions are copied from old file, so license
entire work under GPL-2.0.

This also adds previously undocumented 32 kHz clock output modelled as
regulators.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211001130249.80405-1-krzysztof.kozlowski@canonical.com


Signed-off-by: Mark Brown <broonie@kernel.org>