drm/atomic-helper: Fix kerneldoc for prepare_planes

Copypaste-fail from cleanup_planes. Reported by Tvrtko.

Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 7715c40..a745881 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1096,9 +1096,9 @@
  */
 
 /**
- * drm_atomic_helper_prepare_planes - prepare plane resources after commit
+ * drm_atomic_helper_prepare_planes - prepare plane resources before commit
  * @dev: DRM device
- * @state: atomic state object with old state structures
+ * @state: atomic state object with new state structures
  *
  * This function prepares plane state, specifically framebuffers, for the new
  * configuration. If any failure is encountered this function will call