TI Wilink 6/7/8 (wl12xx/wl18xx) SDIO devices

This node provides properties for controlling the wilink wireless device. The
node is expected to be specified as a child node to the SDIO controller that
connects the device to the system.

Required properties:
 - compatible: should be one of the following:
    * "ti,wl1271"
    * "ti,wl1273"
    * "ti,wl1281"
    * "ti,wl1283"
    * "ti,wl1285"
    * "ti,wl1801"
    * "ti,wl1805"
    * "ti,wl1807"
    * "ti,wl1831"
    * "ti,wl1835"
    * "ti,wl1837"
 - interrupts : specifies attributes for the out-of-band interrupt.

Optional properties:
 - ref-clock-frequency : ref clock frequency in Hz
 - tcxo-clock-frequency : tcxo clock frequency in Hz

Note: the *-clock-frequency properties assume internal clocks. In case of external
clock, new bindings (for parsing the clock nodes) have to be added.

Example:

&mmc3 {
	vmmc-supply = <&wlan_en_reg>;
	bus-width = <4>;
	cap-power-off-card;
	keep-power-in-suspend;

	#address-cells = <1>;
	#size-cells = <0>;
	wlcore: wlcore@2 {
		compatible = "ti,wl1835";
		reg = <2>;
		interrupt-parent = <&gpio0>;
		interrupts = <19 IRQ_TYPE_LEVEL_HIGH>;
	};
};