dt-bindings: usb: dwc3: Add Realtek DHC RTD SoC DWC3 USB

Document the DWC3 USB bindings for Realtek SoCs.

Signed-off-by: Stanley Chang <stanley_chang@realtek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230826031028.1892-2-stanley_chang@realtek.com


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