MdePkg: Change function parameter type

MdePkg: Change function parameter type

Change type of parameter Opcode from UINT16 to UINTN
in EFI_S3_SAVE_STATE_WRITE and EFI_S3_SAVE_STATE_INSERT.
According to PI 1.6(Errata A), the type of Opcode in
EFI_S3_SAVE_STATE_WRITE and EFI_S3_SAVE_STATE_INSERT should
be UINTN not UINT16.
https://bugzilla.tianocore.org/show_bug.cgi?id=1517

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>