Remove NRF52BoardOTA class and integrate it into NRF52Board

As all NRF52 boards now have OTA support, let's remove the subclass
and integrate it into the base class.

Signed-off-by: Frieder Schrempf <frieder@fris.de>

variants/wio_wm1110/WioWM1110Board.h

@@ -11,9 +11,9 @@
 #endif
 #define Serial Serial1
 
-class WioWM1110Board : public NRF52BoardDCDC, public NRF52BoardOTA {
+class WioWM1110Board : public NRF52BoardDCDC {
 public:
-  WioWM1110Board() : NRF52BoardOTA("WM1110_OTA") {}
+  WioWM1110Board() : NRF52Board("WM1110_OTA") {}
   void begin();
 
 #if defined(LED_GREEN)