variants: Heltec T114: Use DC/DC regulator

The schematic shows the LC circuit for the internal DC/DC regulator
to be available. Enable it to save power.

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

variants/heltec_t114/T114Board.h

@@ -9,7 +9,7 @@
 #define  PIN_BAT_CTL      6
 #define  MV_LSB   (3000.0F / 4096.0F) // 12-bit ADC with 3.0V input range
 
-class T114Board : public NRF52BoardOTA {
+class T114Board : public NRF52BoardDCDC, public NRF52BoardOTA {
 public:
     T114Board() : NRF52BoardOTA("T114_OTA") {}
   void begin();