dt-bindings: phy: cdns,salvo: add property cdns,usb2-disconnect-threshold-microvolt

Add cdns,usb2-disconnect-threshold-microvolt property to address fake USB
disconnection issue during enumeration or suspend state for difference
platform.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20230517161646.3418250-7-Frank.Li@nxp.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>