fuse: fix typo for fuse_permission comment

Found by chance while working on support for idmapped mounts in fuse.
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/dir.c

@@ -1493,7 +1493,7 @@ static int fuse_perm_getattr(struct inode *inode, int mask)
  *
  * 1) Local access checking ('default_permissions' mount option) based
  * on file mode.  This is the plain old disk filesystem permission
- * modell.
+ * model.
  *
  * 2) "Remote" access checking, where server is responsible for
  * checking permission in each inode operation.  An exception to this