UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile to mNumberToFinish
UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile to mNumberToFinish

Add volatile qualifier to mNumberToFinish to prevent GCC 5.4
compiler from optimizing away required logic in ACPI S3 resume.

Cc: Liming Gao <6480311aeeb4b006862f6d13ebabddc03f51e507@intel.com>
Cc: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Cc: Andrew Fish <be8d29debaaf5173b4b7ecb4ace852732e71f7b9@apple.com>
Cc: Jeff Fan <7d6fed0251a47076d6e691789131f22f07d057b4@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <fd20bc543a9f65bb633fac7d08a403c1f1c8eb6c@intel.com>
Reviewed-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Reviewed-by: Jeff Fan <7d6fed0251a47076d6e691789131f22f07d057b4@intel.com>

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