Repeater and other power optimizations (#2999)

* End wire if we find no i2c devices

* Set tx-power to 0 on nrf bluetooth shutdown

* Change polling interval of PowerFSM to 100ms instead of 10ms

* Guard 3v3

src/PowerFSMThread.h

@@ -33,7 +33,7 @@ class PowerFSMThread : public OSThread
             powerFSM.trigger(EVENT_SHUTDOWN);
         }
 
-        return 10;
+        return 100;
     }
 };