dt-bindings: mips: Document Loongson kvm guest board

Document loongson64v-4core-virtio, a virtio based kvm guest board for
Loongson-3.

Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: Jiaxun Yang <[email protected]>
Signed-off-by: Thomas Bogendoerfer <[email protected]>

Author: chenhuacai

Documentation/devicetree/bindings/mips/loongson/devices.yaml

@@ -32,4 +32,8 @@ properties:
       - description: Generic Loongson64 Quad Core + LS7A
         items:
           - const: loongson,loongson64g-4core-ls7a
+
+      - description: Virtual Loongson64 Quad Core + VirtIO
+        items:
+          - const: loongson,loongson64v-4core-virtio
 ...