dt-bindings: usb: generic-ehci: Document clock-names in top-level

Convention is to always have properties defined in top-level part of the
binding and then customized (narrowed per variant) in "if:then:" blocks.
The clock-names were mentioned only in such "if:then:" block for
atmel,at91sam9g45-ehci, thus add the top-level part and disallow usage
of clock-names for other devices.  This has no practical impact as
clock-names are not used by other variants, except in
hisilicon/hi3798cv200.dtsi, but that SoC has it undocumented.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260625091744.109467-3-krzysztof.kozlowski@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/generic-ehci.yaml

@@ -98,6 +98,10 @@ properties:
         - if a USB DRD channel: first clock should be host and second
           one should be peripheral
 
+  clock-names:
+    minItems: 1
+    maxItems: 4
+
   power-domains:
     maxItems: 1
 
@@ -186,6 +190,9 @@ allOf:
       required:
         - clocks
         - clock-names
+    else:
+      properties:
+        clock-names: false
 
 unevaluatedProperties: false