dt-bindings: intc: Convert ingenic,intc.txt to YAML

Convert the ingenic,intc.txt doc file to ingenic,intc.yaml.

Some compatible strings now require a fallback, as the controller
generally works the same across the SoCs families.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Rob Herring <robh@kernel.org>