MdeModulePkg/S3SaveState: cast Position for S3BootScriptLib explicitly

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>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>