esp32/network_lan: Add support for LAN8710 PHY.

LAN8710 uses the same drivers as LAN8720, so this commit just adds the
names.  Alternatively, both could be summarised under LAN87xx, like the
esp-idf does.
diff --git a/ports/esp32/modnetwork.c b/ports/esp32/modnetwork.c
index 7429274..cc066f3 100644
--- a/ports/esp32/modnetwork.c
+++ b/ports/esp32/modnetwork.c
@@ -261,6 +261,7 @@
     #endif
 
     #if (ESP_IDF_VERSION_MAJOR == 4) && (ESP_IDF_VERSION_MINOR >= 1) && (CONFIG_IDF_TARGET_ESP32)
+    { MP_ROM_QSTR(MP_QSTR_PHY_LAN8710), MP_ROM_INT(PHY_LAN8710) },
     { MP_ROM_QSTR(MP_QSTR_PHY_LAN8720), MP_ROM_INT(PHY_LAN8720) },
     { MP_ROM_QSTR(MP_QSTR_PHY_IP101), MP_ROM_INT(PHY_IP101) },
     { MP_ROM_QSTR(MP_QSTR_PHY_RTL8201), MP_ROM_INT(PHY_RTL8201) },
diff --git a/ports/esp32/modnetwork.h b/ports/esp32/modnetwork.h
index 7bcfa0e..5d1c3aa 100644
--- a/ports/esp32/modnetwork.h
+++ b/ports/esp32/modnetwork.h
@@ -28,7 +28,7 @@
 
 #include "esp_event.h"
 
-enum { PHY_LAN8720, PHY_IP101, PHY_RTL8201, PHY_DP83848, PHY_KSZ8041 };
+enum { PHY_LAN8710, PHY_LAN8720, PHY_IP101, PHY_RTL8201, PHY_DP83848, PHY_KSZ8041 };
 enum { ETH_INITIALIZED, ETH_STARTED, ETH_STOPPED, ETH_CONNECTED, ETH_DISCONNECTED, ETH_GOT_IP };
 
 // Cases similar to ESP8266 user_interface.h
diff --git a/ports/esp32/network_lan.c b/ports/esp32/network_lan.c
index c57d781..3cd1efc 100644
--- a/ports/esp32/network_lan.c
+++ b/ports/esp32/network_lan.c
@@ -125,7 +125,8 @@
     }
     self->phy_addr = args[ARG_phy_addr].u_int;
 
-    if (args[ARG_phy_type].u_int != PHY_LAN8720 &&
+    if (args[ARG_phy_type].u_int != PHY_LAN8710 &&
+        args[ARG_phy_type].u_int != PHY_LAN8720 &&
         args[ARG_phy_type].u_int != PHY_IP101 &&
         args[ARG_phy_type].u_int != PHY_RTL8201 &&
         #if ESP_IDF_VERSION_MINOR >= 3      // KSZ8041 is new in ESP-IDF v4.3
@@ -146,6 +147,7 @@
     self->phy = NULL;
 
     switch (args[ARG_phy_type].u_int) {
+        case PHY_LAN8710:
         case PHY_LAN8720:
             self->phy = esp_eth_phy_new_lan8720(&phy_config);
             break;