firewire: core: optimize propagation of BROADCAST_CHANNEL

Cache the test result of whether a device implements BROADCAST_CHANNEL.
This minimizes traffic on the bus after each bus reset.  A majority of
devices does not implement BROADCAST_CHANNEL.

Remove busy retries; just rely on the hardware to retry requests to busy
responders.  Remove unnecessary log messages.

Rename the flag is_irm to broadcast_channel_allocated to better reflect
its meaning.  Reset the flag earlier in fw_core_handle_bus_reset.

Pass the generation down as a call parameter; that way generation can't
be newer than card->broadcast_channel_allocated and device->node_id.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/fw-topology.c

@@ -526,6 +526,7 @@ void fw_core_handle_bus_reset(struct fw_card *card, int node_id, int generation,
 
 	spin_lock_irqsave(&card->lock, flags);
 
+	card->broadcast_channel_allocated = false;
 	card->node_id = node_id;
 	/*
 	 * Update node_id before generation to prevent anybody from using