numa: add -numa node,memdev= option

This option provides the infrastructure for binding guest NUMA nodes
to host NUMA nodes.  For example:

 -object memory-ram,size=1024M,policy=bind,host-nodes=0,id=ram-node0 \
 -numa node,nodeid=0,cpus=0,memdev=ram-node0 \
 -object memory-ram,size=1024M,policy=interleave,host-nodes=1-3,id=ram-node1 \
 -numa node,nodeid=1,cpus=1,memdev=ram-node1

The option replaces "-numa node,mem=".

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

MST: conflict resolution
diff --git a/qapi-schema.json b/qapi-schema.json
index e65b7b1..e05f8ba 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3119,8 +3119,12 @@
 # @cpus: #optional VCPUs belonging to this node (assign VCPUS round-robin
 #         if omitted)
 #
-# @mem: #optional memory size of this node (equally divide total memory among
-#        nodes if omitted)
+# @mem: #optional memory size of this node; mutually exclusive with @memdev.
+#       Equally divide total memory among nodes if both @mem and @memdev are
+#       omitted.
+#
+# @memdev: #optional memory backend object.  If specified for one node,
+#          it must be specified for all nodes.
 #
 # Since: 2.1
 ##
@@ -3128,4 +3132,5 @@
   'data': {
    '*nodeid': 'uint16',
    '*cpus':   ['uint16'],
-   '*mem':    'size' }}
+   '*mem':    'size',
+   '*memdev': 'str' }}