Fix coverity issue 'Uninitialized scalar variable"

There are three boolean variable which were not initialized and later
being used in the code.
Signed-off-by: Yacov Simhony <ysimhony@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -513,7 +513,7 @@ static void macb_validate(struct phylink_config *config,
 	struct net_device *ndev = to_net_dev(config->dev);
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(mask) = { 0, };
 	struct macb *bp = netdev_priv(ndev);
-	bool have_1g, have_sgmii, have_10g;
+	bool have_1g=false, have_sgmii=false, have_10g=false;
 
 	/* Determine what modes are supported */
 	if (macb_is_gem(bp) &&