1) Add package description file (dec) for PcAtChipsetPkg
2) Add Pcd8259LegacyModeMask for platform developer configure default mask value in legacy mode.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8749 6f19259b-4bc3-4df7-8a09-765794883524
3 files changed