CoffeeLakeSiliconPkg: TcoWdtHob.h Cleanup

Removes duplicate EFI_HOB_GENERIC_HEADER and EFI_HOB_GUID_TYPE
definitions from TcoWdtHob.h

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Michael Kubacki <michael.a.kubacki@intel.com>
Cc: Sai Chaganty <rangasai.v.chaganty@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>
Reviewed-by: Sai Chaganty <rangasai.v.chaganty@intel.com>