node: add flags to port_use_buffer

Remove the CAN_USE_BUFFERS flag, it is redundant. We can know this
because of the IO params and buffer params.

Add flags to the port_use_buffer call. We also want this call to
replace port_alloc_buffer. Together with a new result event we can
ask the node to (a)synchronously fill up the buffer data for us. This
is part of a plan to let remote nodes provide buffer data.

src/extensions/client-node.h

@@ -171,6 +171,7 @@ struct pw_client_node_proxy_events {
 				  enum spa_direction direction,
 				  uint32_t port_id,
 				  uint32_t mix_id,
+				  uint32_t flags,
 				  uint32_t n_buffers,
 				  struct pw_client_node_buffer *buffers);
 	/**