KabylakeOpenBoardPkg/KBLRvp3: Remove the consume of 8259-related PCD

For KabylakeRvp3, none of its consumed modules is using the PCD:
gPcAtChipsetPkgTokenSpaceGuid.Pcd8259LegacyModeMask

Thus, this commit will remove the PCD consumption in the DSC file.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Michael Kubacki <michael.a.kubacki@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>