dt-bindings: display: lt9611: Support single Port B input

The LT9611 has two DSI input ports (Port A and Port B). Update the
binding to clearly document the port mapping and allow using Port B
alone when DSI is physically connected to Port B only.

Changes:
- Clarify port@0 corresponds to DSI Port A input
- Clarify port@1 corresponds to DSI Port B input
- Change port requirement from mandatory port@0 to anyOf port@0/port@1,
  allowing either port to be used independently

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Hongyang Zhao <hongyang.zhao@thundersoft.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Roger Shimizu <rosh@debian.org>
Tested-by: Roger Shimizu <rosh@debian.org>
Link: https://patch.msgid.link/20260207-rubikpi-next-20260116-v3-1-23b9aa189a3a@thundersoft.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml

@@ -44,21 +44,28 @@ properties:
       port@0:
         $ref: /schemas/graph.yaml#/properties/port
         description:
-          Primary MIPI port-1 for MIPI input
+          DSI Port A input. directly drives the display, or works in
+          combination with Port B for higher resolution displays.
 
       port@1:
         $ref: /schemas/graph.yaml#/properties/port
         description:
-          Additional MIPI port-2 for MIPI input, used in combination
-          with primary MIPI port-1 to drive higher resolution displays
+          DSI Port B input. Can be used alone if DSI is physically
+          connected to Port B, or in combination with Port A for higher
+          resolution displays.
 
       port@2:
         $ref: /schemas/graph.yaml#/properties/port
         description:
           HDMI port for HDMI output
 
+    anyOf:
+      - required:
+          - port@0
+      - required:
+          - port@1
+
     required:
-      - port@0
       - port@2
 
 required: