dt-bindings: display: bridge: it66121: Add compatible string for IT6610

Add a new ite,it6610 compatible string to the IT66121 binding
documentation, since the two chips are very similar.
Signed-off-by: NPaul Cercueil <paul@crapouillou.net>
Reviewed-by: NRobert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221214125821.12489-2-paul@crapouillou.net

Documentation/devicetree/bindings/display/bridge/ite,it66121.yaml

@@ -17,7 +17,9 @@ description: |
 
 properties:
   compatible:
-    const: ite,it66121
+    enum:
+      - ite,it66121
+      - ite,it6610
 
   reg:
     maxItems: 1