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: I448969b10b0e29f44ca2b7949472ea21c63ffb3a
Signed-off-by: Vijayanand Jitta <quic_vjitta@quicinc.com>