KabylakeOpenBoardPkg: Remove PeiMain for Dispatch mode.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1916



In Dispatch mode PeiMain from FSP Binary will be launched
so the one from boot loader can be removed.

Test: Verified the PeiMain is removed in Dispatch mode
      and included in API mode.

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