Doxygen comments for enum & structure

Added doxygen comments for enums & structures for user & channel
layers.

Unit-test:
verified build.

Change-Id: Ie5af8d6cdd4c04cb396869b7a3dc44f84efedd19
Signed-off-by: Richard Marian Thomaiyar <richard.marian.thomaiyar@linux.intel.com>
diff --git a/user_channel/user_layer.hpp b/user_channel/user_layer.hpp
index 956c925..ce985df 100644
--- a/user_channel/user_layer.hpp
+++ b/user_channel/user_layer.hpp
@@ -22,6 +22,9 @@
 {
 
 // TODO: Has to be replaced with proper channel number assignment logic
+/**
+ * @enum Channel Id
+ */
 enum class EChannelID : uint8_t
 {
     chanLan1 = 0x01
@@ -33,6 +36,11 @@
 static constexpr uint8_t ipmiMaxUsers = 15;
 static constexpr uint8_t ipmiMaxChannels = 16;
 
+/** @struct PrivAccess
+ *
+ *  User privilege related access data as per IPMI specification.(refer spec
+ * sec 22.26)
+ */
 struct PrivAccess
 {
 #if BYTE_ORDER == LITTLE_ENDIAN