KabylakeOpenBoardPkg: Add support for PcdFspDispatchModeUseFspPeiMain

If PcdFspDispatchModeUseFspPeiMain is FALSE, then the BoardPkg
should include PeiMain in FvPreMemory.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Michael Kubacki <michael.a.kubacki@intel.com>
Signed-off-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Michael Kubacki <michael.a.kubacki@intel.com>