dt-bindings: mfd: max77620: Add compatible for Maxim 77663

Maxim 77663 has a few minor differences in regards to hardware interface
and available capabilities by comparing it with 77620 and 20024 models,
hence re-use 77620 device-tree binding for the 77663.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>