Add one wrapper implementation over assembly RdRand access to check possible NULL parameter, for better alignment with comment description. Cc: Liming Gao <liming.gao@intel.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Qin Long <qin.long@intel.com> Reviewed-by: Liming Gao <liming.gao@intel.com>