net: dsa.h: drop duplicate word in comment

Drop doubled word "to" in a comment.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/dsa.h

@@ -612,7 +612,7 @@ struct dsa_switch_ops {
 	 * MTU change functionality. Switches can also adjust their MRU through
 	 * this method. By MTU, one understands the SDU (L2 payload) length.
 	 * If the switch needs to account for the DSA tag on the CPU port, this
-	 * method needs to to do so privately.
+	 * method needs to do so privately.
 	 */
 	int	(*port_change_mtu)(struct dsa_switch *ds, int port,
 				   int new_mtu);