Revert "dt-bindings: phy: Add documentation for NSP USB3 PHY"

This reverts commit c8ca631f ("dt-bindings: phy: Add documentation
for NSP USB3 PHY") to match reverting commit adding the new PHY driver.
Please note we revert this commit before it reached stable release.

If new compatible string is needed it should be added to the existing
bcm-ns-usb3-phy.txt which already describes this PHY.
Acked-by: Jon Mason <jon.mason@broadcom.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

Documentation/devicetree/bindings/phy/brcm,nsp-usb3-phy.txt

-Broadcom USB3 phy binding for northstar plus SoC
-The USB3 phy is internal to the SoC and is accessed using mdio interface.
-
-Required mdio bus properties:
-- reg: Should be 0x0 for SoC internal USB3 phy
-- #address-cells: must be 1
-- #size-cells: must be 0
-
-Required USB3 PHY properties:
-- compatible: should be "brcm,nsp-usb3-phy"
-- reg: USB3 Phy address on SoC internal MDIO bus and it should be 0x10.
-- usb3-ctrl-syscon: handler of syscon node defining physical address
-  of usb3 control register.
-- #phy-cells: must be 0
-
-Required usb3 control properties:
-- compatible: should be "brcm,nsp-usb3-ctrl"
-- reg: offset and length of the control registers
-
-Example:
-
-	mdio@0 {
-		reg = <0x0>;
-		#address-cells = <1>;
-		#size-cells = <0>;
-
-		usb3_phy: usb-phy@10 {
-			compatible = "brcm,nsp-usb3-phy";
-			reg = <0x10>;
-			usb3-ctrl-syscon = <&usb3_ctrl>;
-			#phy-cells = <0>;
-			status = "disabled";
-		};
-	};
-
-	usb3_ctrl: syscon@104408 {
-		compatible = "brcm,nsp-usb3-ctrl", "syscon";
-		reg = <0x104408 0x3fc>;
-	};