drm/bridge: imx: Add LDB support for i.MX8qxp

This patch adds a drm bridge driver for i.MX8qxp LVDS display bridge(LDB)
which is officially named as pixel mapper.  The LDB has two channels.
Each of them supports up to 24bpp parallel input color format and can map
the input to VESA or JEIDA standards.  The two channels cannot be used
simultaneously, that is to say, the user should pick one of them to use.
Two LDB channels from two LDB instances can work together in LDB split
mode to support a dual link LVDS display.  The channel indexes have to be
different.  Channel0 outputs odd pixels and channel1 outputs even pixels.
This patch supports the LDB single mode and split mode.

Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com> # Colibri iMX8X, LT170410-2WHC, LP156WF1
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220611141421.718743-12-victor.liu@nxp.com