debugfs: fix missing mutex_destroy() in short_fops case

we need that in ->real_fops == NULL, ->short_fops != NULL case

Fixes: 8dc6d81 "debugfs: add small file operations for most files"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20241229081223.3193228-1-viro@zeniv.linux.org.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Al Viro

fs/debugfs/inode.c

@@ -229,7 +229,7 @@ static void debugfs_release_dentry(struct dentry *dentry)
 		return;
 
 	/* check it wasn't a dir (no fsdata) or automount (no real_fops) */
-	if (fsd && fsd->real_fops) {
+	if (fsd && (fsd->real_fops || fsd->short_fops)) {
 		WARN_ON(!list_empty(&fsd->cancellations));
 		mutex_destroy(&fsd->cancellations_mtx);
 	}