IB/uverbs: Free uapi on destroy

Make sure we free struct uverbs_api once we clean the radix tree. It was
allocated by uverbs_alloc_api().

Fixes: 9ed3e5f44772 ("IB/uverbs: Build the specs into a radix tree at runtime")
Reported-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/uverbs_uapi.c

@@ -248,6 +248,7 @@ void uverbs_destroy_api(struct uverbs_api *uapi)
 		kfree(rcu_dereference_protected(*slot, true));
 		radix_tree_iter_delete(&uapi->radix, &iter, slot);
 	}
+	kfree(uapi);
 }
 
 struct uverbs_api *uverbs_alloc_api(