drm/imx/dcss: Call drm_atomic_helper_shutdown() at shutdown time

Based on grepping through the source code this driver appears to be
missing a call to drm_atomic_helper_shutdown() at system shutdown
time. Among other things, this means that if a panel is in use that it
won't be cleanly powered off at system shutdown time.

The fact that we should call drm_atomic_helper_shutdown() in the case
of OS shutdown/restart comes straight out of the kernel doc "driver
instance overview" in drm_drv.c.

Suggested-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Reviewed-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230921122641.RFT.v2.1.I134336fce7eac5a63bdac46d57b0888858fc8081@changeid

drm/imx/dcss: use drm_bridge_connector API

Make use of drm_bridge_connector API to have the connector initialized by the
display controller.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@nxp.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200731081836.3048-4-laurentiu.palcu@oss.nxp.com

drm/imx: Add initial support for DCSS on iMX8MQ

This adds initial support for iMX8MQ's Display Controller Subsystem (DCSS).
Some of its capabilities include:
* 4K@60fps;
* HDR10;
* one graphics and 2 video pipelines;
* on-the-fly decompression of compressed video and graphics;

The reference manual can be found here:
https://www.nxp.com/webapp/Download?colCode=IMX8MDQLQRM

The current patch adds only basic functionality: one primary plane for
graphics, linear, tiled and super-tiled buffers support (no graphics
decompression yet), no HDR10 and no video planes.

Video planes support and HDR10 will be added in subsequent patches once
per-plane de-gamma/CSC/gamma support is in.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@nxp.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200731081836.3048-3-laurentiu.palcu@oss.nxp.com