dt-bindings: mfd: Add MAX5970 and MAX5978

The MAX597x is a hot swap controller with configurable fault protection.
It also has 10bit ADC for current & voltage measurements.

...
Changes in V12:
- Update title

Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
Co-developed-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Co-developed-by: Naresh Solanki <Naresh.Solanki@9elements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230307121246.127425-1-Naresh.Solanki@9elements.com