dt-bindings: phy: Add Freescale i.MX8qm Mixel LVDS PHY binding

Add bindings for Mixel LVDS PHY found on Freescale i.MX8qm SoC.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://lore.kernel.org/r/20220706034810.2352641-3-victor.liu@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>