QTI QRTR MHI transport binding

- compatible:
	Usage: required
	Value type: <stringlist>
	Definition: must be "qcom,qrtr-mhi"
			    "qcom,qrtr-mhi-dev"

- qcom,dev-id:
	Usage: optional
	Value type: <u32>
	Definition: indicates the dev-id that this transport is for. Should be
		    passed into the qrtr core logic to determine to match with the
		    dev-id used by the mhi controller.

- qcom,net-id:
	Usage: optional
	Value type: <u32>
	Definition: indicates what subnet this transport belongs to. If the dev-id
		    passed above matches the one passed into qrtr logic by mhi core,
		    then this net-id is passed into the qrtr core logic to determin
		    if forwarding is needed on this endpoint.

- qcom,low-latency:
	Usage: optional
	Value type: <bool>
	Definition: indicates whether this transport receiving thread needs to
		    be set to realtime priority for enhanced performance.

= EXAMPLE
The following example represents the qrtr mhi transport node on a device
configured as a pcie endpoint and needs to forward data from the host to a
slpi co-processor.

	mhi_qrtr_cnss {
		compatible = "qcom,qrtr-mhi";
		qcom,dev-id = <0x1103>;
		qcom,net-id = <0>;
		qcom,low-latency;
	};