AP_HAL_ESP32: UARTDriver: move vprintf

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>

libraries/AP_HAL_ESP32/UARTDriver.h

@@ -42,8 +42,6 @@ class ESP32::UARTDriver : public AP_HAL::UARTDriver
     /* Do not allow copies */
     CLASS_NO_COPY(UARTDriver);
 
-    void vprintf(const char *fmt, va_list ap) override;
-
     bool is_initialized() override;
     bool tx_pending() override;
 
@@ -90,6 +88,8 @@ class ESP32::UARTDriver : public AP_HAL::UARTDriver
 
     uint32_t get_baud_rate() const override { return _baudrate; }
 
+    void vprintf(const char *fmt, va_list ap) override;
+
 private:
     bool _initialized;
     const size_t TX_BUF_SIZE = 1024;