dsa: Add stub tag driver put method

When a DSA switch driver is unloaded, the lock on the tag driver
should be released so the module can be unloaded. Add the needed calls,
but leave the actual release code as a stub.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>

v2

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index 0a68d78..54e89c9 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -137,6 +137,10 @@ const struct dsa_device_ops *dsa_tag_driver_get(int tag_protocol)
 	return ops;
 }
 
+void dsa_tag_driver_put(const struct dsa_device_ops *ops)
+{
+}
+
 static int dev_is_class(struct device *dev, void *class)
 {
 	if (dev->class != NULL && !strcmp(dev->class->name, class))