I2C for Atmel platforms

Required properties :
- compatible : Must be "atmel,at91rm9200-i2c", "atmel,at91sam9261-i2c",
     "atmel,at91sam9260-i2c", "atmel,at91sam9g20-i2c", "atmel,at91sam9g10-i2c",
     "atmel,at91sam9x5-i2c", "atmel,sama5d4-i2c" or "atmel,sama5d2-i2c"
- reg: physical base address of the controller and length of memory mapped
     region.
- interrupts: interrupt number to the cpu.
- #address-cells = <1>;
- #size-cells = <0>;
- clocks: phandles to input clocks.

Optional properties:
- clock-frequency: Desired I2C bus frequency in Hz, otherwise defaults to 100000
- dmas: A list of two dma specifiers, one for each entry in dma-names.
- dma-names: should contain "tx" and "rx".
- atmel,fifo-size: maximum number of data the RX and TX FIFOs can store for FIFO
  capable I2C controllers.
- i2c-sda-hold-time-ns: TWD hold time, only available for "atmel,sama5d4-i2c"
  and "atmel,sama5d2-i2c".
- Child nodes conforming to i2c bus binding

Examples :

i2c0: i2c@fff84000 {
	compatible = "atmel,at91sam9g20-i2c";
	reg = <0xfff84000 0x100>;
	interrupts = <12 4 6>;
	#address-cells = <1>;
	#size-cells = <0>;
	clocks = <&twi0_clk>;
	clock-frequency = <400000>;

	24c512@50 {
		compatible = "24c512";
		reg = <0x50>;
		pagesize = <128>;
	}
}

i2c0: i2c@f8034600 {
	compatible = "atmel,sama5d2-i2c";
	reg = <0xf8034600 0x100>;
	interrupts = <19 IRQ_TYPE_LEVEL_HIGH 7>;
	dmas = <&dma0
		(AT91_XDMAC_DT_MEM_IF(0) | AT91_XDMAC_DT_PER_IF(1))
		AT91_XDMAC_DT_PERID(11)>,
	       <&dma0
		(AT91_XDMAC_DT_MEM_IF(0) | AT91_XDMAC_DT_PER_IF(1))
		AT91_XDMAC_DT_PERID(12)>;
	dma-names = "tx", "rx";
	#address-cells = <1>;
	#size-cells = <0>;
	clocks = <&flx0>;
	atmel,fifo-size = <16>;
	i2c-sda-hold-time-ns = <336>;

	wm8731: wm8731@1a {
		compatible = "wm8731";
		reg = <0x1a>;
	};
};
