dt-bindings: usb: add layerscape super speed usb support

Add missed binding doc for layerscape dwc3 usb controller.

Fix below warning:
arch/arm64/boot/dts/freescale/fsl-ls1028a-kontron-kbox-a-230-ls.dtb: /soc/usb@3100000:
	failed to match any schema with compatible: ['fsl,ls1028a-dwc3', 'snps,dwc3']

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240815152159.4177782-1-Frank.Li@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>