Move the I8042 macro close to the TYPE_I8042 define.

This will make future conversion to OBJECT_DECLARE* easier.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Tested-By: Roman Bolshakov <r.bolshakov@yadro.com>
Message-Id: <20200825192110.3528606-34-ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>