doxygen: add groups for all modules

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

src/mic/mic.h

@@ -35,13 +35,18 @@ struct thresholdContext {
 
 namespace upm {
 
+/**
+ * @brief analog microphone library
+ * @defgroup mic libupm-mic
+ */
+
 /**
  * @brief C++ API for Microphone
  *
  * This file defines the Microphone Analog sensor
  *
+ * @ingroup mic
  * @snippet mic-example.cxx Interesting
- *
  */
 class Microphone {
     public: