doxygen: add groups for all modules

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

src/my9221/my9221.h

@@ -37,11 +37,17 @@
 
 namespace upm {
 
+/**
+ * @brief my9221 led bar library
+ * @defgroup my9221 libupm-9221
+ */
+
 /**
  * @brief C++ API for MY9221 led bar module
  *
  * This file defines the MY9221 C++ interface for libmy9221
  *
+ * @ingroup my9221
  * @snippet led-bar.cxx Interesting
  */
 class MY9221 {