dt-bindings: irqchip: Add node name to PRUSS INTC

dt-bindings: irqchip: Add node name to PRUSS INTC

The current PRUSS Interrupt Controller binding doesn't exactly specify
the convention for the node name. These interrupt-controllers will always
have a unit address. Update the binding with the '$nodename' using the
expected generic name, this shall ensure the interrupt-controller.yaml
is automatically applied to this binding.

Signed-off-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20210126163251.29468-1-s-anna@ti.com
Signed-off-by: Rob Herring <robh@kernel.org>