nrf: port: call common_hal_rtc_init() during init

Call the new function to set the RTC, or reset it if the offset is not
valid.

Signed-off-by: Sean Cross <sean@xobs.io>

ports/nrf/supervisor/port.c

@@ -120,6 +120,10 @@ safe_mode_t port_init(void) {
     // Configure millisecond timer initialization.
     tick_init();
 
+#if CIRCUITPY_RTC
+    common_hal_rtc_init();
+#endif
+
 #if CIRCUITPY_ANALOGIO
     analogin_init();
 #endif