Move device code from main.cpp to earlyInitVariant (#9438)

variants/nrf52840/heltec_mesh_solar/variant.cpp

@@ -19,6 +19,7 @@
 */
 
 #include "variant.h"
+#include "Arduino.h"
 #include "nrf.h"
 #include "wiring_constants.h"
 #include "wiring_digital.h"
@@ -38,3 +39,10 @@ void initVariant()
     digitalWrite(PIN_SCREEN_VDD_CTL, LOW); // Start with power on
 #endif
 }
+
+void variant_shutdown()
+{
+    nrf_gpio_cfg_default(PIN_GPS_PPS);
+    detachInterrupt(PIN_GPS_PPS);
+    detachInterrupt(PIN_BUTTON1);
+}