llvm: Fixed remaining warnings for llvm

This commit addresses warnings emitted from the llvm
compilers which were not encountered with gnu.

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/bmpx8x/bmpx8x.hpp

@@ -196,7 +196,6 @@ class BMPX8X : public IPressureSensor, public ITemperatureSensor {
         std::string m_name;
 
         int m_controlAddr;
-        int m_bus;
         mraa::I2c m_i2ControlCtx;
 
         uint8_t oversampling;