drm/mipi-dbi: Provide callbacks for atomic interfaces

drm/mipi-dbi: Provide callbacks for atomic interfaces

Refactor the existing simple-display callbacks such that they invoke
helpers compatible with regular atomic modesetting. Allows for adding
mipi-dbi drives that do not require simple-display helpers.

Provide initializer macro for elements of the regular modesetting
pipeline. These will be used by drivers to integrate mipi-dbi helpers.
Also provide initializer macros for the plane formats.

As the new helpers are DRM functions, add the drm_ prefix. Mipi-dbi
interfaces currently lack this.

v3:
- fix uninitialized variable (David)
- document public interfaces (David)
- mention format macros in commit message (David)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: David Lechner <david@lechnology.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260319160110.109610-4-tzimmermann@suse.de