dt-bindings: i2c: xiic: Add 'xlnx,axi-iic-2.1' to compatible

Add xilinx I2C new version 'xlnx,axi-iic-2.1' string to compatible.
Add clock-frequency as optional property.

Signed-off-by: Raviteja Narayanam <raviteja.narayanam@xilinx.com>
Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Documentation/devicetree/bindings/i2c/xlnx,xps-iic-2.00.a.yaml

@@ -14,7 +14,9 @@ allOf:
 
 properties:
   compatible:
-    const: xlnx,xps-iic-2.00.a
+    enum:
+      - xlnx,axi-iic-2.1
+      - xlnx,xps-iic-2.00.a
 
   reg:
     maxItems: 1
@@ -30,6 +32,13 @@ properties:
     description: |
       Input clock name.
 
+  clock-frequency:
+    description:
+      Optional I2C SCL clock frequency. If not specified, do not configure
+      in software, rely only on hardware design value.
+    default: 100000
+    enum: [ 100000, 400000, 1000000 ]
+
 required:
   - compatible
   - reg