[FL-1190] Enable OTG pullup for reading and writing keys (#423)

applications/ibutton/helpers/key-writer.cpp

@@ -10,10 +10,12 @@ KeyWriter::Error KeyWriter::write(iButtonKey* key) {
 }
 
 void KeyWriter::start() {
+    api_hal_power_enable_otg();
     onewire_master->start();
 }
 
 void KeyWriter::stop() {
+    api_hal_power_disable_otg();
     onewire_master->stop();
 }