s390x/cpumodel: Fix harmless misuse of visit_check_struct()

s390x/cpumodel: Fix harmless misuse of visit_check_struct()

Commit e47970f51d "s390x/cpumodel: Fix query-cpu-model-FOO error API
violations" neglected to change visit_check_struct()'s Error **
argument along with the others.  If visit_check_struct() failed, we'd
take the success path.  Fortunately, it can't fail here:
qobject_input_check_struct() checks we consumed the whole dictionary,
and to get here, we did.  Fix it anyway.

Cc: David Hildenbrand <david@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200505101908.6207-4-armbru@redhat.com>