regulator: dt-bindings: Add binding schema for mt6357 regulators

Add YAML schema for the MediaTek MT6357 regulators.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>
Link: https://lore.kernel.org/r/20221005-mt6357-support-v7-2-477e60126749@baylibre.com


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