UefiCpuPkg/PiSmmCpuDxeSmm: clear exec file mode bits on "PiSmmCpuDxeSmm.c"

UefiCpuPkg/PiSmmCpuDxeSmm: clear exec file mode bits on "PiSmmCpuDxeSmm.c"

Commit 241f914975d5 ("UefiCpuPkg/PiSmmCpuDxeSmm: Add support for PCD
PcdPteMemoryEncryptionAddressOrMask", 2017-03-01) unintentionally set the
executable file mode bits on "PiSmmCpuDxeSmm.c"; clear them now.

Cc: Eric Dong <eric.dong@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1092
Fixes: 241f914975d50e34f6da57d1e5ac60eedb5d52de
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>