Some socs have a large number of interrupts requests to service
the needs of its many peripherals and subsystems. All of the
interrupt lines from the subsystems are not needed at the same
time, so they have to be muxed to the irq-controller appropriately.
In such places a interrupt controllers are preceded by an CROSSBAR
that provides flexibility in muxing the device requests to the controller
inputs.

Required properties:
- compatible : Should be "ti,irq-crossbar"
- reg: Base address and the size of the crossbar registers.
- ti,max-irqs: Total number of irqs available at the interrupt controller.
- ti,reg-size: Size of a individual register in bytes. Every individual
	    register is assumed to be of same size. Valid sizes are 1, 2, 4.
- ti,irqs-reserved: List of the reserved irq lines that are not muxed using
		 crossbar. These interrupt lines are reserved in the soc,
		 so crossbar bar driver should not consider them as free
		 lines.

Examples:
		crossbar_mpu: @4a020000 {
			compatible = "ti,irq-crossbar";
			reg = <0x4a002a48 0x130>;
			ti,max-irqs = <160>;
			ti,reg-size = <2>;
			ti,irqs-reserved = <0 1 2 3 5 6 131 132 139 140>;
		};