Remove unused variable attribute flag.

Signed off by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed by: Jeff Fan <jeff.fan@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Contributed-under: TianoCore Contribution Agreement 1.0


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15321 6f19259b-4bc3-4df7-8a09-765794883524