net: designware: fix unused warning when CONFIG_DW_AUTONEG is enabled

The ctrl variable is only used when autoneg support is disabled, so only
declare it under those conditions to avoid an unused variable warning.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Reviewed-by: Vipin Kumar <vipin.kumar@st.com>

drivers/net/designware.c

@@ -368,11 +368,13 @@ static int configure_phy(struct eth_device *dev)
 {
 	struct dw_eth_dev *priv = dev->priv;
 	int phy_addr;
-	u16 bmcr, ctrl;
+	u16 bmcr;
 #if defined(CONFIG_DW_AUTONEG)
 	u16 bmsr;
 	u32 timeout;
 	u16 anlpar, btsr;
+#else
+	u16 ctrl;
 #endif
 
 #if defined(CONFIG_DW_SEARCH_PHY)