merge compilation fix for WifiSta.cpp and Eth.cpp

See espressif/esp32-arduino-lib-builder#12
for more

Author: alorbach

Diff for: libraries/WiFi/src/ETH.cpp

@@ -193,8 +193,8 @@ IPAddress ETHClass::gatewayIP()
 
 IPAddress ETHClass::dnsIP(uint8_t dns_no)
 {
-    ip_addr_t dns_ip = dns_getserver(dns_no);
-    return IPAddress(dns_ip.u_addr.ip4.addr);
+	const ip_addr_t* dns_ip = dns_getserver(dns_no);
+    return IPAddress(dns_ip->u_addr.ip4.addr);	
 }
 
 IPAddress ETHClass::broadcastIP()

Diff for: libraries/WiFi/src/WiFiSTA.cpp

@@ -488,8 +488,8 @@ IPAddress WiFiSTAClass::dnsIP(uint8_t dns_no)
     if(WiFiGenericClass::getMode() == WIFI_MODE_NULL){
         return IPAddress();
     }
-    ip_addr_t dns_ip = dns_getserver(dns_no);
-    return IPAddress(dns_ip.u_addr.ip4.addr);
+	const ip_addr_t* dns_ip = dns_getserver(dns_no);
+    return IPAddress(dns_ip->u_addr.ip4.addr);
 }
 
 /**