MdeModulePkg VariableDxe: Correct address pointers from AuthVariableLib

MdeModulePkg VariableDxe: Correct address pointers from AuthVariableLib

Originally, the double pointer (VOID **) is not correct for convert
address pointers from AuthVariableLib.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <Jiewen.Yao@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18054 6f19259b-4bc3-4df7-8a09-765794883524