net: dsa: Simplify 'dsa_tag_protocol_to_str()'

There is no point in preparing the module name in a buffer. The format
string can be passed diectly to 'request_module()'.

This axes a few lines of code and cleans a few things:
   - max len for a driver name is MODULE_NAME_LEN wich is ~ 60 chars,
     not 128. It would be down-sized in 'request_module()'
   - we should pass the total size of the buffer to 'snprintf()', not the
     size minus 1

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa.c

@@ -88,13 +88,9 @@ const struct dsa_device_ops *dsa_tag_driver_get(int tag_protocol)
 {
 	struct dsa_tag_driver *dsa_tag_driver;
 	const struct dsa_device_ops *ops;
-	char module_name[128];
 	bool found = false;
 
-	snprintf(module_name, 127, "%s%d", DSA_TAG_DRIVER_ALIAS,
-		 tag_protocol);
-
-	request_module(module_name);
+	request_module("%s%d", DSA_TAG_DRIVER_ALIAS, tag_protocol);
 
 	mutex_lock(&dsa_tag_drivers_lock);
 	list_for_each_entry(dsa_tag_driver, &dsa_tag_drivers_list, list) {