x86/CPUID: fill all fields in x86_cpuid_policy_fill_native()

x86/CPUID: fill all fields in x86_cpuid_policy_fill_native()

Coverity validly complains that the new call from
tools/tests/cpu-policy/test-cpu-policy.c:test_cpuid_current() leaves
two fields uninitialized, yet they get then consumed by
x86_cpuid_copy_to_buffer(). (All other present callers of the function
pass a pointer to a static - and hence initialized - buffer.)

Coverity-ID: 1464809
Fixes: c22ced93e167 ("tests/cpu-policy: Confirm that CPUID serialisation is sorted")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Paul Durrant <paul@xen.org>