net: l3mdev: Fix kerneldoc warning

net/l3mdev/l3mdev.c:249: warning: Function parameter or member 'arg' not described in 'l3mdev_fib_rule_match'
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20201028005059.930192-1-andrew@lunn.chSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/l3mdev/l3mdev.c

@@ -241,6 +241,7 @@ EXPORT_SYMBOL_GPL(l3mdev_link_scope_lookup);
  *				L3 master device
  *	@net: network namespace for device index lookup
  *	@fl:  flow struct
+ *	@arg: store the table the rule matched with here
  */
 
 int l3mdev_fib_rule_match(struct net *net, struct flowi *fl,