debugfs: fix missing mutex_destroy() in short_fops case

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

Fixes: 8dc6d81c6b2a "debugfs: add small file operations for most files"
Signed-off-by: Al Viro <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

fs/debugfs/inode.c

···
 		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);
 	}