Add the device-tree node for the mem-offline driver to enable
memory offlining and convey the sizes of the offlineable memory.
Describe the communication channel used to communicate with the
firmware which supports onlining and offlining of memory.
Change-Id: I6c7868545fe7601d3cc2c6d5ea95c980046c52b4
Signed-off-by: Vijayanand Jitta <quic_vjitta@quicinc.com>