Add comments to clarify mPubKeyStore buffer MemCopy. There is no memory overflow issue.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Chao, Zhang <chao.b.zhang@intel.com>
Reviewed-by: Yao, Jiewen <jiewen.yao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16227 6f19259b-4bc3-4df7-8a09-765794883524