"avx-vvni" was introduced to qemu in commit
c1826ea6a052084f2e6a0bae9dd5932a727df039, adding it Cooperlake.
This feature is currently not used by any libvirt CPU models, but its
addition silences a warning from sync_qemu_i386.py:
```
warning: Unknown feature 'CPUID_7_1_EAX_AVX_VNNI'
warning: Feature unknown to libvirt: CPUID_7_1_EAX_AVX_VNNI
```
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
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