1. Remove any references on other files from DebugTimer.c, to avoid un-used symbols linked.
2. Add GLOBAL_REMOVE_IF_UNREFERENCED for all global variables.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>






git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16298 6f19259b-4bc3-4df7-8a09-765794883524