According to UEFI spec, unsupported function should return EFI_UNSUPPORTED
directly.
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>