defconfig: sm8150: Enable memory region offlining support

Add support for DDR power management through the dynamic memory
offline framework. This driver interfaces between the memory
hotplug subsystem and AOP which hot adds or removes memory blocks
and controls the start/stop of refresh of these DDR regions. This
helps reduce power consumption by avoiding refresh for offlined
memory blocks.

Change-Id: I81b5b41dac3c015d5f90f7144030f5e9e4ced39d
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>