dt-bindings: usb: Drop unneeded quotes

Cleanup bindings dropping unneeded quotes. Once all these are fixed,
checking for this can be enabled in yamllint.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230320233904.2920197-1-robh@kernel.org


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