Adjust ADC scaling based on kernel version

The older Linux 3.8.13 kernel produced raw ADC value of 0 to 1800. Newer Linux 4.1+ kernels produce ADC value of 0 to 4095.

Author: pdp7

source/py_adc.c

@@ -86,7 +86,11 @@ static PyObject *py_read(PyObject *self, PyObject *args)
  }
 
  //scale modifier
+#ifdef BBBVERSION41
  value = value / 4095.0;
+#else
+ value = value / 1800.0;
+#endif
 
  py_value = Py_BuildValue("f", value);