dt-bindings: phy: mtk-xs-phy: support type switch by pericfg

Add support for type switch by pericfg register between USB3/PCIe.

Signed-off-by: Frank Wunderlich <[e-mail]>
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/phy/mediatek,xsphy.yaml

···
         minimum: 1
         maximum: 31
 
+      mediatek,syscon-type:
+        $ref: /schemas/types.yaml#/definitions/phandle-array
+        description:
+          A phandle to syscon used to access the register of type switch,
+          the field should always be 3 cells long.
+        items:
+          - items:
+              - description:
+                  Phandle to phy type configuration system controller
+              - description:
+                  Phy type configuration register offset
+              - description:
+                  Index of config segment
+                enum: [0, 1, 2, 3]
+
     required:
       - reg
       - clocks