Update logs and doxygen for vpd-tool

This commit updates the following for vpd-tool,
* Removed duplicate success log for write keyword command.
* Updated the doxygen for readKeyword API.
* Error logs are enabled in all places until verbose mode is
implemented.

Change-Id: Ica201694fc87445d4cd368875d1414140c77b236
Signed-off-by: Anupama B R <anupama.b.r1@ibm.com>
diff --git a/vpd-tool/include/tool_utils.hpp b/vpd-tool/include/tool_utils.hpp
index fece0ec..e4b0a33 100644
--- a/vpd-tool/include/tool_utils.hpp
+++ b/vpd-tool/include/tool_utils.hpp
@@ -376,10 +376,6 @@
 
     l_result.read(l_rc);
 
-    if (l_rc > 0)
-    {
-        std::cout << "Data updated successfully " << std::endl;
-    }
     return l_rc;
 }
 
@@ -540,7 +536,7 @@
     catch (const sdbusplus::exception::SdBusError& l_ex)
     {
         // TODO: log only when verbose is enabled
-        // std::cerr << std::string(l_ex.what()) << std::endl;
+        std::cerr << std::string(l_ex.what()) << std::endl;
     }
     return l_serviceInfMap;
 }