fix for cyw43_wrappers.h build with C code

Author: lyusupov

cores/rp2040/cyw43_wrappers.h

@@ -23,11 +23,15 @@
 #include <pico/cyw43_driver.h>
 
 extern bool __isPicoW;
+#ifdef __cplusplus
 extern "C" {
+#endif
     void init_cyw43_wifi();
     void __lockBluetooth();
     void __unlockBluetooth();
     void cyw43_pinMode(pin_size_t pin, PinMode mode);
     void cyw43_digitalWrite(pin_size_t pin, PinStatus val);
     PinStatus cyw43_digitalRead(pin_size_t pin);
+#ifdef __cplusplus
 }
+#endif