hw/arm/virt: Add nvdimm hotplug support

hw/arm/virt: Add nvdimm hotplug support

This adds support for nvdimm hotplug events through GED
and enables nvdimm for the arm/virt. Now Guests with ACPI
can have both cold and hot plug of nvdimms.

Hot removal functionality is not yet supported.

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20200421125934.14952-5-shameerali.kolothum.thodi@huawei.com>
Acked-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>