WhiskeylakeOpenBoardPkg/WhiskeylakeURvp: Update FSP base PCDs

Sets the FSP-T, FSP-M, and FSP-S base address PCDs based on the flash map.

Previously these were hardcoded in the DSC file.

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