Features/Intel/UserInterface/UserAuthFeaturePkg: Add RngLib instance to DSC

The UserAuthFeaturePkg build currently fails since it does not specify
a RngLib instance and OpensslLib links against RngLib.

Cc: Dandan Bi <dandan.bi@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>