OMAP2+ McSPI device

Required properties:
- compatible :
  - "ti,am654-mcspi" for AM654.
  - "ti,omap2-mcspi" for OMAP2 & OMAP3.
  - "ti,omap4-mcspi" for OMAP4+.
- ti,spi-num-cs : Number of chipselect supported  by the instance.
- ti,hwmods: Name of the hwmod associated to the McSPI
- ti,pindir-d0-out-d1-in: Select the D0 pin as output and D1 as
			  input. The default is D0 as input and
			  D1 as output.

Optional properties:
- dmas: List of DMA specifiers with the controller specific format
	as described in the generic DMA client binding. A tx and rx
	specifier is required for each chip select.
- dma-names: List of DMA request names. These strings correspond
	1:1 with the DMA specifiers listed in dmas. The string naming
	is to be "rxN" and "txN" for RX and TX requests,
	respectively, where N equals the chip select number.

Examples:

[hwmod populated DMA resources]

mcspi1: mcspi@1 {
    #address-cells = <1>;
    #size-cells = <0>;
    compatible = "ti,omap4-mcspi";
    ti,hwmods = "mcspi1";
    ti,spi-num-cs = <4>;
};

[generic DMA request binding]

mcspi1: mcspi@1 {
    #address-cells = <1>;
    #size-cells = <0>;
    compatible = "ti,omap4-mcspi";
    ti,hwmods = "mcspi1";
    ti,spi-num-cs = <2>;
    dmas = <&edma 42
	    &edma 43
	    &edma 44
	    &edma 45>;
    dma-names = "tx0", "rx0", "tx1", "rx1";
};
