dt-bindings: usb: ti,keystone-dwc3: drop assigned-clocks

The meta schema from DT schema already defines assigned-clocks, so there
is no need for device schema to mention it at all. There are also no
benefits of having it here.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/usb/ti,keystone-dwc3.yaml

···
     minItems: 1
     maxItems: 2
 
-  assigned-clocks:
-    minItems: 1
-    maxItems: 2
-
-  assigned-clock-parents:
-    minItems: 1
-    maxItems: 2
-
   power-domains:
     maxItems: 1
     description: Should contain a phandle to a PM domain provider node