dt-bindings: phy: Convert ti,keystone-usbphy to DT schema

Convert the TI Keystone USB PHY binding to DT schema format. Drop the
"#address-cells" and "#size-cells" properties which don't make sense
without any child nodes.

Signed-off-by: Rob Herring (Arm) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/phy/keystone-usb-phy.txt

···
-TI Keystone USB PHY
-
-Required properties:
- - compatible: should be "ti,keystone-usbphy".
- - #address-cells, #size-cells : should be '1' if the device has sub-nodes
-   with 'reg' property.
- - reg : Address and length of the usb phy control register set.
-
-The main purpose of this PHY driver is to enable the USB PHY reference clock
-gate on the Keystone SOC for both the USB2 and USB3 PHY. Otherwise it is just
-an NOP PHY driver.  Hence this node is referenced as both the usb2 and usb3
-phy node in the USB Glue layer driver node.
-
-usb_phy: usb_phy@2620738 {
-	compatible = "ti,keystone-usbphy";
-	#address-cells = <1>;
-	#size-cells = <1>;
-	reg = <0x2620738 32>;
-};

Documentation/devicetree/bindings/phy/ti,keystone-usbphy.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/phy/ti,keystone-usbphy.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TI Keystone USB PHY
+
+maintainers:
+  - Nishanth Menon <[e-mail]>
+  - Santosh Shilimkar <[e-mail]>
+
+description:
+  The main purpose of this PHY driver is to enable the USB PHY reference clock
+  gate on the Keystone SOC for both the USB2 and USB3 PHY. Otherwise it is just
+  an NOP PHY driver. Hence this node is referenced as both the usb2 and usb3
+  phy node in the USB Glue layer driver node.
+
+properties:
+  compatible:
+    const: ti,keystone-usbphy
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    usb-phy@2620738 {
+        compatible = "ti,keystone-usbphy";
+        reg = <0x2620738 32>;
+    };