dt-bindings: qcom-sps-dma: Add snapshot of SPS DMA driver

* Qualcomm technologies inc, DMA engine driver for BAM (Bus Access Manager).

Required properties:

- compatible: Should be "qcom,sps-dma".

- reg: Should contain DMA registers location and length. This should include

  all of the per-channel registers.

- interrupts: Should contain the BAM interrupt number.

- qcom,summing-threshold:  Should contain the BAM event threshold of

  the sum of descriptors' sizes in bytes.

Optional properties:

- qcom,managed-locally : Use when BAM global device control is managed locally

  by the application processor.

Example:

	dma_blsp1: qcom,sps-dma@f9904000 { /* BLSP1 */

		#dma-cells = <4>;

		compatible = "qcom,sps-dma";

		reg = <0xf9904000 0x19000>;

		interrupts = <0 238 0>;

		qcom,summing-threshold = <10>;

	};

DMA clients connected to the qcom-sps-dma DMA controller must use the format

described in the dma.txt file, using a five-cell specifier for each channel,

a phandle plus four integer cells, as shown below:

dmas = <[phandle of the dma controller] [pipe index] [number of descriptors]

				[sps_connect flags] [sps_register_event flags]>;

Example:

i2c_2: i2c@f9924000 { /* BLSP1 QUP2 */

	.

	.

	.

	/*     <&phandle pipe-idx n-descs connect-flags event-flags> */

	dmas = <&dma_blsp1 14 32 0x20000020 0x20>,

	       <&dma_blsp1 15 64 0x20000020 0x20>;

	dma-names = "tx", "rx";

};