phy: freescale: phy-fsl-imx8-mipi-dphy: Add i.MX8qxp LVDS PHY mode support

i.MX8qxp SoC embeds a Mixel MIPI DPHY + LVDS PHY combo which supports
either a MIPI DSI display or a LVDS display.  The PHY mode is controlled
by SCU firmware and the driver would call a SCU firmware function to
configure the PHY mode.  The single LVDS PHY has 4 data lanes to support
a LVDS display.  Also, with a master LVDS PHY and a slave LVDS PHY, they
may work together to support a LVDS display with 8 data lanes(usually, dual
LVDS link display).  Note that this patch supports the LVDS PHY mode only
for the i.MX8qxp Mixel combo PHY, i.e., the MIPI DPHY mode is yet to be
supported, so for now error would be returned from ->set_mode() if MIPI
DPHY mode is passed over to it for the combo PHY.

Cc: Guido Günther <agx@sigxcpu.org>
Cc: Robert Chiras <robert.chiras@nxp.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Reviewed-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://lore.kernel.org/r/20220419010852.452169-6-victor.liu@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>