UefiCpuPkg/SmmCpuFeaturesLib: Rename SmmCpuFeaturesLib.c

UefiCpuPkg/SmmCpuFeaturesLib: Rename SmmCpuFeaturesLib.c

This change renames SmmCpuFeaturesLib.c to SmmCpuFeaturesLibCommon.c
to better convey that this file contains library implementation
common to all library instances.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Message-Id: <20210217213227.1277-3-mikuback@linux.microsoft.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>