regulator: Add binding for Richtek RT5759 DCDC converter

Add bindings for Richtek RT5759 high-performance DCDC converter.

Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/1648294788-11758-2-git-send-email-u0084500@gmail.com


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