Shared Memory Time Stamp Driver

Provides a high response mechanism that allows for AP to get
timestamp from mDSP. It provides the device node in /dev/
for user to read the timestamp, and the timestamp is transferred
through smd between mDSP and AP.

The devicetree representation of the SPM block should be:

Required properties

- compatible: "qcom,smd-ts".
- ts-channel-name: The string corresponding to the channel name of the
			peripheral subsystem.
- ch-channel-type: The interal SMD edge for this subsystem found in
			<soc/qcom/smd.h>

Example:

	qcom,smd-ts {
		compatible = "qcom,smd-ts";
		ts-channel-name = "vsync_ts_diff";
		ts-channel-type = <0>; /* SMD_APPS_MODEM */
	};