drm/ast: Fix comment on modeset lock

The ast driver protects the commit tail against concurrent reads
of the display modes by acquiring a lock. The comment is misleading
as the lock is not released in atomic_flush, but at the end of the
commit-tail helper. Rewrite the comment.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 1fe1821 ("drm/ast: Acquire I/O-register lock in atomic_commit_tail function")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.2+
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250324094520.192974-2-tzimmermann@suse.de

Author: tdz

drivers/gpu/drm/ast/ast_mode.c

@@ -939,9 +939,9 @@ static void ast_mode_config_helper_atomic_commit_tail(struct drm_atomic_state *s
 
 	/*
 	 * Concurrent operations could possibly trigger a call to
-	 * drm_connector_helper_funcs.get_modes by trying to read the
-	 * display modes. Protect access to I/O registers by acquiring
-	 * the I/O-register lock. Released in atomic_flush().
+	 * drm_connector_helper_funcs.get_modes by reading the display
+	 * modes. Protect access to registers by acquiring the modeset
+	 * lock.
 	 */
 	mutex_lock(&ast->modeset_lock);
 	drm_atomic_helper_commit_tail(state);