dt-bindings: MIPS: Add entry for the YLM RetroMini

Add an entry to ingenic/devices.yaml for the JZ4725B-based
YLM "RetroMini" RS-90.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

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

@@ -22,6 +22,11 @@ properties:
           - const: qi,lb60
           - const: ingenic,jz4740
 
+      - description: YLM RetroMini RS-90
+        items:
+          - const: ylm,rs90
+          - const: ingenic,jz4725b
+
       - description: Game Consoles Worldwide GCW Zero
         items:
           - const: gcw,zero