documentation: dt-bindings: mem-offline: Add doc for mem-offline driver

Memory offline driver

=====================

The memory offline driver supports the onlining and offlining of DDR memory.

Through the mem-offline node you can configure how much of the DDR will

support being offlined/onlined.

By default all memory is onlined when the device has booted up.

Note that offlinable memory can only support 'movable' memory allocations so

designating too much memory as offlinable can result in system performance and

stability issues.

For more information on how to request the onlining and offlining of memory

see the memory hotplug documentation (Documentation/memory-hotplug.txt).

Required properties:

- compatible: "qcom,mem-offline"

- granule: The minimum granule size in mega-bytes for memory onlining/offlining.

- mem-percent: Percentage of the DDR which will support being onlined/offlined.

	The system will round down the value to align with the minimum offlinable

	granule size supported by DDR.

Example:

  mem-offline {

	compatible = "qcom,mem-offline";

	granule = <512>;

	mem-percent = "35";

  };