ADI AXI-I2S controller

The core can be generated with transmit (playback), only receive
(capture) or both directions enabled.

Required properties:
 - compatible : Must be "adi,axi-i2s-1.00.a"
 - reg : Must contain I2S core's registers location and length
 - clocks : Pairs of phandle and specifier referencing the controller's clocks.
   The controller expects two clocks, the clock used for the AXI interface and
   the clock used as the sampling rate reference clock sample.
 - clock-names : "axi" for the clock to the AXI interface, "ref" for the sample
   rate reference clock.
 - dmas: Pairs of phandle and specifier for the DMA channels that are used by
   the core. The core expects two dma channels if both transmit and receive are
   enabled, one channel otherwise.
 - dma-names : "tx" for the transmit channel, "rx" for the receive channel.

For more details on the 'dma', 'dma-names', 'clock' and 'clock-names' properties
please check:
	* resource-names.txt
	* clock/clock-bindings.txt
	* dma/dma.txt

Example:

	i2s: i2s@77600000 {
		compatible = "adi,axi-i2s-1.00.a";
		reg = <0x77600000 0x1000>;
		clocks = <&clk 15>, <&audio_clock>;
		clock-names = "axi", "ref";
		dmas = <&ps7_dma 0>, <&ps7_dma 1>;
		dma-names = "tx", "rx";
	};
