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


git-svn-id: 5648d1bec6962b0a6d1d1b40eba8cf5cdb62da3d@8750 6f19259b-4bc3-4df7-8a09-765794883524

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2