dt-bindings: usb: samsung-hsotg: remove bindings already part of dwc2

samsung,s3c6400-hsotg compatible is already fully covered in dwc2.yaml
bindings.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230722201620.35489-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/usb/samsung-hsotg.txt

-Samsung High Speed USB OTG controller
------------------------------
-
-The Samsung HSOTG IP can be found on Samsung SoCs, from S3C6400 onwards.
-It gives functionality of OTG-compliant USB 2.0 host and device with
-support for USB 2.0 high-speed (480Mbps) and full-speed (12 Mbps)
-operation.
-
-Currently only device mode is supported.
-
-Binding details
------
-
-Required properties:
-- compatible: "samsung,s3c6400-hsotg" should be used for all currently
-    supported SoC,
-- interrupts: specifier of interrupt signal of interrupt controller,
-    according to bindings of interrupt controller,
-- clocks: contains an array of clock specifiers:
-    - first entry: OTG clock
-- clock-names: contains array of clock names:
-    - first entry: must be "otg"
-- vusb_d-supply: phandle to voltage regulator of digital section,
-- vusb_a-supply: phandle to voltage regulator of analog section.
-
-Example
------
-
-	hsotg@12480000 {
-		compatible = "samsung,s3c6400-hsotg";
-		reg = <0x12480000 0x20000>;
-		interrupts = <0 71 0>;
-		clocks = <&clock 305>;
-		clock-names = "otg";
-		vusb_d-supply = <&vusb_reg>;
-		vusb_a-supply = <&vusbdac_reg>;
-	};
-