Provide dummy CYW43 callbacks when no WiFi used (#681)

Fixes #680

cores/rp2040/sdkoverride/cyw43_arch_threadsafe_background.c

@@ -316,4 +316,34 @@ void cyw43_arch_poll() {
     //    }
 }
 
+#ifdef ARDUINO_RASPBERRY_PI_PICO_W
+void __attribute__((weak)) cyw43_cb_tcpip_init(cyw43_t *self, int itf);
+void cyw43_cb_tcpip_init(cyw43_t *self, int itf) {
+    (void) self;
+    (void) itf;
+}
+void __attribute__((weak)) cyw43_cb_tcpip_deinit(cyw43_t *self, int itf);
+void cyw43_cb_tcpip_deinit(cyw43_t *self, int itf) {
+    (void) self;
+    (void) itf;
+}
+void __attribute__((weak)) cyw43_cb_tcpip_set_link_up(cyw43_t *self, int itf);
+void cyw43_cb_tcpip_set_link_up(cyw43_t *self, int itf) {
+    (void) self;
+    (void) itf;
+}
+void __attribute__((weak)) cyw43_cb_tcpip_set_link_down(cyw43_t *self, int itf);
+void cyw43_cb_tcpip_set_link_down(cyw43_t *self, int itf) {
+    (void) self;
+    (void) itf;
+}
+void __attribute__((weak)) cyw43_cb_process_ethernet(void *cb_data, int itf, size_t len, const uint8_t *buf);
+void cyw43_cb_process_ethernet(void *cb_data, int itf, size_t len, const uint8_t *buf) {
+    (void) cb_data;
+    (void) itf;
+    (void) len;
+    (void) buf;
+}
+#endif
+
 #endif