drm/atomic: Make the drm_atomic_state documentation less ambiguous

The current documentation of drm_atomic_state says that it's the "global
state object". This is confusing since, while it does contain all the
objects affected by an update and their respective states, if an object
isn't affected by this update it won't be part of it.

Thus, it's not truly a "global state", unlike object state structures
that do contain the entire state of a given object.

Reviewed-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Link: https://lore.kernel.org/r/20231214100917.277842-4-mripard@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

include/drm/drm_atomic.h

@@ -346,7 +346,13 @@ struct __drm_private_objs_state {
 };
 
 /**
- * struct drm_atomic_state - the global state object for atomic updates
+ * struct drm_atomic_state - Atomic commit structure
+ *
+ * This structure is the kernel counterpart of @drm_mode_atomic and represents
+ * an atomic commit that transitions from an old to a new display state. It
+ * contains all the objects affected by the atomic commit and both the new
+ * state structures and pointers to the old state structures for
+ * these.
  *
  * States are added to an atomic update by calling drm_atomic_get_crtc_state(),
  * drm_atomic_get_plane_state(), drm_atomic_get_connector_state(), or for