net-next: stmmac: Remove unnecessary parenthesis

Signed-off-by: NCorentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -789,7 +789,7 @@ static void stmmac_adjust_link(struct net_device *dev)
 		 * If not, we operate in half-duplex mode. */
 		if (phydev->duplex != priv->oldduplex) {
 			new_state = true;
-			if (!(phydev->duplex))
+			if (!phydev->duplex)
 				ctrl &= ~priv->hw->link.duplex;
 			else
 				ctrl |= priv->hw->link.duplex;