net: dsa: mv88e6xxx: missing unlock on error path

We added a new error path, but we need to drop the lock before we return.

Fixes: 2d2e1dd29962 ("net: dsa: mv88e6xxx: Cache the port cmode")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 1775231..8da3d39 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -2408,7 +2408,7 @@ static int mv88e6xxx_setup(struct dsa_switch *ds)
 		if (chip->info->ops->port_get_cmode) {
 			err = chip->info->ops->port_get_cmode(chip, i, &cmode);
 			if (err)
-				return err;
+				goto unlock;
 
 			chip->ports[i].cmode = cmode;
 		}