dt-bindings: usb: ci-hdrc-usb2: add fsl,picophy-rise-fall-time-adjust property

The fsl,picophy-rise-fall-time-adjust property can help to adjust the
rise/fall times of the high-speed transmitter waveform. The value can be
0~3. It has no unit. According to the description of USBNC_n_PHY_CFG1
register, the rise/fall time will be increased or decreased by a certain
percentage relative to design default time if a value is given to this
property.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Peter Chen <peter.chen@kernel.org>
Link: https://lore.kernel.org/r/20230627112126.1882666-2-xu.yang_2@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>