dt-bindings: phy: qcom,snps-eusb2-repeater: Add magic tuning overrides

The EUSB2 repeater requires some alterations to its init sequence,
depending on board design.

Add support for making the necessary changes to that sequence to make USB
functional on SM8550-based Xperia 1 V.

They all have lackluster description due to lack of information.
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230830-topic-eusb2_override-v2-1-7d8c893d93f6@linaro.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml

@@ -32,6 +32,27 @@ properties:
 
   vdd3-supply: true
 
+  qcom,tune-usb2-disc-thres:
+    $ref: /schemas/types.yaml#/definitions/uint8
+    description: High-Speed disconnect threshold
+    minimum: 0
+    maximum: 7
+    default: 0
+
+  qcom,tune-usb2-amplitude:
+    $ref: /schemas/types.yaml#/definitions/uint8
+    description: High-Speed trasmit amplitude
+    minimum: 0
+    maximum: 15
+    default: 8
+
+  qcom,tune-usb2-preem:
+    $ref: /schemas/types.yaml#/definitions/uint8
+    description: High-Speed TX pre-emphasis tuning
+    minimum: 0
+    maximum: 7
+    default: 5
+
 required:
   - compatible
   - reg