MdeModulePkg/S3SaveState: cast Position for S3BootScriptLib explicitly
    
    The BootScriptInsert() and BootScriptLabel() functions take the in/out
    parameter "Position" as (EFI_S3_BOOT_SCRIPT_POSITION*), and pass it to
    S3BootScriptMoveLastOpcode() and S3BootScriptLabel(), respectively.
    
    The callees take the in/out parameter "Position" as (VOID**). Add explicit
    casts for clarity.
    
    There is no change in functionality.
    
    Cc: Dandan Bi <dandan.bi@intel.com>
    Cc: Eric Dong <eric.dong@intel.com>
    Cc: Hao A Wu <hao.a.wu@intel.com>
    Cc: Jian J Wang <jian.j.wang@intel.com>
    Cc: Liming Gao <liming.gao@intel.com>
    Cc: Ray Ni <ray.ni@intel.com>
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>