AC97 link bindings

These bindings can be included within any other device node.

Required properties:
 - pinctrl-names: Has to contain following states to setup the correct
   pinmuxing for the used gpios:
	"ac97-running": AC97-link is active
	"ac97-reset": AC97-link reset state
	"ac97-warm-reset": AC97-link warm reset state
 - ac97-gpios: List of gpio phandles with args in the order ac97-sync,
   ac97-sdata, ac97-reset


Example:

ssi {
	...

	pinctrl-names = "default", "ac97-running", "ac97-reset", "ac97-warm-reset";
	pinctrl-0 = <&ac97link_running>;
	pinctrl-1 = <&ac97link_running>;
	pinctrl-2 = <&ac97link_reset>;
	pinctrl-3 = <&ac97link_warm_reset>;
	ac97-gpios = <&gpio3 20 0 &gpio3 22 0 &gpio3 28 0>;

	...
};
