Add type cast to avoid sign extension on x64 tip.

signed-off-by: Jeff Fan <jeff.fan@intel.com>
reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13709 6f19259b-4bc3-4df7-8a09-765794883524
1 file changed