Picochip picoXcell SPAcc (Security Protocol Accelerator) bindings

Picochip picoXcell devices contain crypto offload engines that may be used for
IPSEC and femtocell layer 2 ciphering.

Required properties:
  - compatible : "picochip,spacc-ipsec" for the IPSEC offload engine
    "picochip,spacc-l2" for the femtocell layer 2 ciphering engine.
  - reg : Offset and length of the register set for this device
  - interrupt-parent : The interrupt controller that controls the SPAcc
    interrupt.
  - interrupts : The interrupt line from the SPAcc.
  - ref-clock : The input clock that drives the SPAcc.

Example SPAcc node:

spacc@10000 {
	compatible = "picochip,spacc-ipsec";
	reg = <0x100000 0x10000>;
	interrupt-parent = <&vic0>;
	interrupts = <24>;
	ref-clock = <&ipsec_clk>, "ref";
};