drm/atomic: Rework the object doc a bit

drm/atomic: Rework the object doc a bit

Commits 63e83c1dba54 ("drm: Consolidate connector arrays in
drm_atomic_state"), b8b5342b699b ("drm: Consolidate plane arrays in
drm_atomic_state") and 5d943aa6c0d4 ("drm: Consolidate crtc arrays in
drm_atomic_state") moved the object pointer and their state pointer to
an intermediate structure storing both.

The CRTC commit didn't update the doc of the crtcs field to reflect
that, and the doc for the planes and connectors fields mention that they
are pointers to an array of structures with per-$OBJECT data.

The private_objs field was added later on by commit b430c27a7de3 ("drm:
Add driver-private objects to atomic state") reusing the same sentence
than the crtcs field, probably due to copy and paste.

While these fields are indeed pointers to an array, each item of that
array contain a pointer to the object structure affected by the update,
and its old and new state. There's no per-object data there, and there's
more than just a pointer to the objects.

Let's rephrase those fields a bit to better match the current situation.

Acked-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://lore.kernel.org/r/20231214100917.277842-3-mripard@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>