*CC2520 IEEE 802.15.4 Compatible Radio*

Required properties:
	- compatible: 		should be "ti,cc2520"
	- spi-max-frequency:	maximal bus speed (8000000), should be set to 4000000 depends
				sync or async operation mode
	- reg:			the chipselect index
	- pinctrl-0: 		pin control group to be used for this controller.
	- pinctrl-names: 	must contain a "default" entry.
	- fifo-gpio:		GPIO spec for the FIFO pin
	- fifop-gpio:		GPIO spec for the FIFOP pin
	- sfd-gpio:		GPIO spec for the SFD pin
	- cca-gpio:		GPIO spec for the CCA pin
	- vreg-gpio:		GPIO spec for the VREG pin
	- reset-gpio:		GPIO spec for the RESET pin
Example:
	cc2520@0 {
		compatible = "ti,cc2520";
		reg = <0>;
		spi-max-frequency = <4000000>;
		pinctrl-names = "default";
		pinctrl-0 = <&cc2520_cape_pins>;
		fifo-gpio = <&gpio1 18 0>;
		fifop-gpio = <&gpio1 19 0>;
		sfd-gpio = <&gpio1 13 0>;
		cca-gpio = <&gpio1 16 0>;
		vreg-gpio = <&gpio0 31 0>;
		reset-gpio = <&gpio1 12 0>;
	};
