add display to station G2 firmwares

variants/station_g2/target.h

@@ -8,11 +8,19 @@
 #include <helpers/AutoDiscoverRTCClock.h>
 #include <helpers/SensorManager.h>
 
+#ifdef DISPLAY_CLASS
+  #include <helpers/ui/SH1106Display.h>
+#endif
+
 extern StationG2Board board;
 extern WRAPPER_CLASS radio_driver;
 extern AutoDiscoverRTCClock rtc_clock;
 extern SensorManager sensors;
 
+#ifdef DISPLAY_CLASS
+  extern DISPLAY_CLASS display;
+#endif
+
 bool radio_init();
 uint32_t radio_get_rng_seed();
 void radio_set_params(float freq, float bw, uint8_t sf, uint8_t cr);