nvdimm: implement NVDIMM device abstract

Introduce "nvdimm" device which is based on pc-dimm device type

Currently, nothing is specific for nvdimm but hotplug is disabled

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/default-configs/i386-softmmu.mak b/default-configs/i386-softmmu.mak
index fb1ad90..b035599 100644
--- a/default-configs/i386-softmmu.mak
+++ b/default-configs/i386-softmmu.mak
@@ -51,6 +51,7 @@
 CONFIG_IOAPIC=y
 CONFIG_PVPANIC=y
 CONFIG_MEM_HOTPLUG=y
+CONFIG_NVDIMM=y
 CONFIG_XIO3130=y
 CONFIG_IOH3420=y
 CONFIG_I82801B11=y