KVM: x86: Advertise AVX-VNNI-INT8 CPUID to user space

KVM: x86: Advertise AVX-VNNI-INT8 CPUID to user space

AVX-VNNI-INT8 is a new set of instructions in the latest Intel platform
Sierra Forest, aims for the platform to have superior AI capabilities.
This instruction multiplies the individual bytes of two unsigned or
unsigned source operands, then adds and accumulates the results into the
destination dword element size operand.

The bit definition:
CPUID.(EAX=7,ECX=1):EDX[bit 4]

AVX-VNNI-INT8 is on a new and sparse CPUID leaf and all bits on this
leaf have no truly kernel use case for now. Given that and to save space
for kernel feature bits, move this new leaf to KVM-only subleaf and plus
an x86_FEATURE definition for AVX-VNNI-INT8 to direct it to the KVM
entry.

Advertise AVX-VNNI-INT8 to KVM userspace. This is safe because there are
no new VMX controls or additional host enabling required for guests to
use this feature.

Signed-off-by: Jiaxi Chen <jiaxi.chen@linux.intel.com>
Message-Id: <20221125125845.1182922-7-jiaxi.chen@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>