REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3833
Add BaseFspDebugLibSerialPort Support for X64.
Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Ashraf Ali S <ashraf.ali.s@intel.com>
Cc: Ted Kuo <ted.kuo@intel.com>
Signed-off-by: Ted Kuo <ted.kuo@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>
Kuo, Ted