Initialize _ledPin (#7487)

* Initialize _ledPin

_ledPin should be initialized to -1 in the constructor to avoid setting a random pin when calling Updater::end without having called Updater::begin before. This happens, for example, in the Homie software

* Fix field sequence

Author: jbliesener

Diff for: cores/esp8266/Updater.cpp

@@ -35,6 +35,7 @@ UpdaterClass::UpdaterClass()
 , _startAddress(0)
 , _currentAddress(0)
 , _command(U_FLASH)
+, _ledPin(-1)
 , _hash(nullptr)
 , _verify(nullptr)
 , _progress_callback(nullptr)