dt-bindings: irqchip: Convert ti, sci-intr bindings to yaml

In order to automate the verification of DT nodes convert
ti,sci-intr.txt ti,sci-intr.yaml.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200806074826.24607-6-lokeshvutla@ti.com