arm64: memory-hotplug: Add MEMORY_HOTPLUG, MEMORY_HOTREMOVE, MEMORY_PROBE

Add memory-hotplug support for ARM64 platform.

This requires addition of
ARCH_ENABLE_MEMORY_HOTPLUG and ARCH_ENABLE_MEMORY_HOTREMOVE config options.

MEMORY_PROBE config option is added to support
/sys/devices/system/memory/probe functionality.

In addition architecture specific arch_add_memory and
arch_remove memory management functions are added.

Change-Id: I1fc4e8c93cfe1b9722b2fc8d811390e6cdfa7995
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Patch-mainline: linux-kernel @ 11 Apr 2017, 18:24
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>
[sudaraja@codeaurora.org: remove explicit zone calculation]
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>