functionfs, gadgetfs: use simple_recursive_removal()

usual mount leaks if something had been bound on top of disappearing
files there.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

drivers/usb/gadget/function/f_fs.c

@@ -2369,8 +2369,7 @@ static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count)
 	for (; count; --count, ++epfile) {
 		BUG_ON(mutex_is_locked(&epfile->mutex));
 		if (epfile->dentry) {
-			d_delete(epfile->dentry);
-			dput(epfile->dentry);
+			simple_recursive_removal(epfile->dentry, NULL);
 			epfile->dentry = NULL;
 		}
 	}

drivers/usb/gadget/legacy/inode.c

@@ -1561,7 +1561,6 @@ static void destroy_ep_files (struct dev_data *dev)
 	spin_lock_irq (&dev->lock);
 	while (!list_empty(&dev->epfiles)) {
 		struct ep_data	*ep;
-		struct inode	*parent;
 		struct dentry	*dentry;
 
 		/* break link to FS */
@@ -1571,7 +1570,6 @@ static void destroy_ep_files (struct dev_data *dev)
 
 		dentry = ep->dentry;
 		ep->dentry = NULL;
-		parent = d_inode(dentry->d_parent);
 
 		/* break link to controller */
 		mutex_lock(&ep->lock);
@@ -1586,10 +1584,7 @@ static void destroy_ep_files (struct dev_data *dev)
 		put_ep (ep);
 
 		/* break link to dcache */
-		inode_lock(parent);
-		d_delete (dentry);
-		dput (dentry);
-		inode_unlock(parent);
+		simple_recursive_removal(dentry, NULL);
 
 		spin_lock_irq (&dev->lock);
 	}