This patch adds a protocol for MockRng. This protocol is used to
mock the Rng protocol for testing purposes.
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Signed-off-by: Doug Flick [MSFT] <doug.edk2@gmail.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
