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/usercommands.hpp b/user_channel/usercommands.hpp
index afbe67a..ea04a26 100644
--- a/user_channel/usercommands.hpp
+++ b/user_channel/usercommands.hpp
@@ -19,7 +19,10 @@
 
 namespace ipmi
 {
-// IPMI commands for user command NETFN:APP.
+
+/**
+ * @enum IPMI commands for user command NETFN:APP.
+ */
 enum ipmi_netfn_user_cmds
 {
     IPMI_CMD_SET_USER_ACCESS = 0x43,
@@ -29,6 +32,9 @@
     IPMI_CMD_SET_USER_PASSWORD = 0x47,
 };
 
+/**
+ * @enum IPMI set password return codes (refer spec sec 22.30)
+ */
 enum class IPMISetPasswordReturnCodes
 {
     ipmiCCPasswdFailMismatch = 0x80,