firewire: normalize a variable name

Standardize on  if (err)
                        handle_error;
           and  if (ret < 0)
                        handle_error;

Don't call a variable err if we store values in it which mean success.
Also, offset some return statements by a blank line since this how we do
it in drivers/firewire.

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 27a3aae..08a7e18 100644
--- a/drivers/firewire/fw-card.c
+++ b/drivers/firewire/fw-card.c
@@ -404,7 +404,7 @@
 {
 	u32 *config_rom;
 	size_t length;
-	int err;
+	int ret;
 
 	card->max_receive = max_receive;
 	card->link_speed = link_speed;
@@ -415,13 +415,14 @@
 	list_add_tail(&card->link, &card_list);
 	mutex_unlock(&card_mutex);
 
-	err = card->driver->enable(card, config_rom, length);
-	if (err < 0) {
+	ret = card->driver->enable(card, config_rom, length);
+	if (ret < 0) {
 		mutex_lock(&card_mutex);
 		list_del(&card->link);
 		mutex_unlock(&card_mutex);
 	}
-	return err;
+
+	return ret;
 }
 EXPORT_SYMBOL(fw_card_add);