Fix build failure of PcAtChipsetPkg.
Fix build failure of PcAtChipsetPkg.

git-svn-id: 5832b8bc916ddbdd95b25464e449aa07e9932e08@13897 6f19259b-4bc3-4df7-8a09-765794883524

hwu25/edk2_PcAtChipsetPkg,hwu25/edk2_PcAtChipsetPkg