dt-bindings: phy: mixel: mipi-dsi-phy: Add Mixel combo PHY support for i.MX8qxp

Add support for Mixel MIPI DPHY + LVDS PHY combo IP
as found on Freescale i.MX8qxp SoC.

Cc: Guido Günther <agx@sigxcpu.org>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: NXP Linux Team <linux-imx@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://lore.kernel.org/r/20220419010852.452169-5-victor.liu@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>