Protect W5500/ENC28J60 isLinked from interrupt (#1805)

Fixes #1786

libraries/lwIP_enc28j60/src/utility/enc28j60.cpp

@@ -39,6 +39,7 @@
 #include <stdio.h>
 #include <stdarg.h>
 #include <string.h>
+#include <LwipEthernet.h>
 
 #include "enc28j60.h"
 
@@ -696,6 +697,8 @@ uint16_t ENC28J60::phyread(uint8_t reg) {
 
 bool ENC28J60::isLinked() {
     // ( https://github.com/JAndrassy/EthernetENC/tree/master/src/utility/enc28j60.h )
-
-    return !!(phyread(MACSTAT2) & 0x400);
+    ethernet_arch_lwip_begin();
+    auto ret = !!(phyread(MACSTAT2) & 0x400);
+    ethernet_arch_lwip_end();
+    return ret;
 }

libraries/lwIP_w5500/src/utility/w5500.h

@@ -38,6 +38,7 @@
 #include <stdint.h>
 #include <Arduino.h>
 #include <SPI.h>
+#include <LwipEthernet.h>
 
 class Wiznet5500 {
 public:
@@ -83,7 +84,10 @@ public:
         @return true when physical link is up
     */
     bool isLinked() {
-        return wizphy_getphylink() == PHY_LINK_ON;
+        ethernet_arch_lwip_begin();
+        auto ret = wizphy_getphylink() == PHY_LINK_ON;
+        ethernet_arch_lwip_end();
+        return ret;
     }
 
     /**