drm/bridge: imx: Add LDB support for i.MX8qm

This patch adds a drm bridge driver for i.MX8qm LVDS display bridge(LDB)
which is officially named as pixel mapper.  The LDB has two channels.
Each of them supports up to 30bpp parallel input color format and can
map the input to VESA or JEIDA standards.  The two channels can be used
simultaneously, either in dual mode or split mode.  In dual mode, the
two channels output identical data.  In split mode, 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/20220611141421.718743-13-victor.liu@nxp.com

drivers/gpu/drm/bridge/imx/Kconfig

+config DRM_IMX8QM_LDB
+	tristate "Freescale i.MX8QM LVDS display bridge"
+	depends on OF
+	depends on COMMON_CLK
+	select DRM_KMS_HELPER
+	help
+	  Choose this to enable the internal LVDS Display Bridge(LDB) found in
+	  Freescale i.MX8qm processor.  Official name of LDB is pixel mapper.
+
 config DRM_IMX8QXP_LDB
 	tristate "Freescale i.MX8QXP LVDS display bridge"
 	depends on OF

drivers/gpu/drm/bridge/imx/Makefile

+imx8qm-ldb-objs := imx-ldb-helper.o imx8qm-ldb-drv.o
+obj-$(CONFIG_DRM_IMX8QM_LDB) += imx8qm-ldb.o
+
 imx8qxp-ldb-objs := imx-ldb-helper.o imx8qxp-ldb-drv.o
 obj-$(CONFIG_DRM_IMX8QXP_LDB) += imx8qxp-ldb.o