ETH: Do not enable DHCP by default.

Leaving DHCP enabled by default leads to race conditions during
address configuration. Disable it by default because it can be
turned on if actually required.

As this fixes the race condition, the 50ms delay to work around it
isn't required anymore.

Author: rtrbt

libraries/Ethernet/src/ETH.cpp

@@ -330,6 +330,7 @@ bool ETHClass::begin(eth_phy_type_t type, int32_t phy_addr, int mdc, int mdio, i
   esp_netif_config.if_key = if_key_str;
   esp_netif_config.if_desc = if_desc_str;
   esp_netif_config.route_prio -= _eth_index * 5;
+  esp_netif_config.flags = (esp_netif_flags_t)(esp_netif_config.flags & ~ESP_NETIF_DHCP_CLIENT);
 
   cfg.base = &esp_netif_config;
 
@@ -418,10 +419,6 @@ bool ETHClass::begin(eth_phy_type_t type, int32_t phy_addr, int mdc, int mdio, i
     }
   }
 
-  // holds a few milliseconds to let DHCP start and enter into a good state
-  // FIX ME -- addresses issue https://github.com/espressif/arduino-esp32/issues/5733
-  delay(50);
-
   return true;
 
 err: