i386: Add new model of Cascadelake-Server

i386: Add new model of Cascadelake-Server

New CPU models mostly inherit features from ancestor Skylake-Server,
while addin new features: AVX512_VNNI, Intel PT.
SSBD support for speculative execution
side channel mitigations.

Note:

On Cascadelake, some capabilities (RDCL_NO, IBRS_ALL, RSBA,
SKIP_L1DFL_VMENTRY and SSB_NO) are enumerated by MSR.
These features rely on MSR based feature support patch.
Will be added later after that patch's in.
http://lists.nongnu.org/archive/html/qemu-devel/2018-09/msg00074.html

Signed-off-by: Tao Xu <tao3.xu@intel.com>
Message-Id: <20180919031122.28487-2-tao3.xu@intel.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>