hw/arm/virt: Add memory hotplug framework

hw/arm/virt: Add memory hotplug framework

This patch adds the memory hot-plug/hot-unplug infrastructure
in machvirt. The device memory is not yet exposed to the Guest
either through DT or ACPI and hence both cold/hot plug of memory
is explicitly disabled for now.

Signed-off-by: Eric Auger <[email protected]>
Signed-off-by: Kwangwoo Lee <[email protected]>
Signed-off-by: Shameer Kolothum <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Reviewed-by: Igor Mammedov <[email protected]>
Message-Id: <20190918130633[email protected]>
Acked-by: Peter Maydell <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>