firewire: core: optimize card shutdown

This fixes a regression by "firewire: keep highlevel drivers attached
during brief connection loss":  There were 2 seconds unnecessary waiting
added to the shutdown procedure of each controller.

We use card->link as status flag to signal the device handler that there
is no use to wait for a come-back.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
diff --git a/drivers/firewire/fw-card.c b/drivers/firewire/fw-card.c
index 17a80ce..7be2cf3 100644
--- a/drivers/firewire/fw-card.c
+++ b/drivers/firewire/fw-card.c
@@ -512,7 +512,7 @@
 	fw_core_initiate_bus_reset(card, 1);
 
 	mutex_lock(&card_mutex);
-	list_del(&card->link);
+	list_del_init(&card->link);
 	mutex_unlock(&card_mutex);
 
 	/* Set up the dummy driver. */