Deduplicate NRF52 startOTAUpdate()

The startOTAUpdate() is the same for all NRF52 boards. Use a common
implementation for all boards that currently have a specific
implementation.

The following boards currently have an empty startOTAUpdate() for
whatever reasons and therefore are not inheriting NRF52BoardOTA to
keep the same state: Nano G2 Ultra, Seeed SenseCAP T1000-E,
Wio WM1110.

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

src/helpers/NRF52Board.h

@@ -27,4 +27,13 @@ class NRF52BoardDCDC : virtual public NRF52Board {
 public:
   virtual void begin() override;
 };
+
+class NRF52BoardOTA : virtual public NRF52Board {
+private:
+  char *ota_name;
+
+public:
+  NRF52BoardOTA(char *name) : ota_name(name) {}
+  virtual bool startOTAUpdate(const char *id, char reply[]) override;
+};
 #endif