dt-bindings: mfd: maxim,max77843: Add MAX77843 bindings

Document the bindings for MAX77843 MFD driver, based on Exynos5433 TM2
devicetree.  These are neither accurate nor finished bindings but at
least allow parsing existing DTS files.

The example DTS was copied from existing DTS
(exynos5433-tm2-common.dtsi), so keep the license as GPL-2.0-only.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220111174805.223732-5-krzysztof.kozlowski@canonical.com