Rename the macros to make them consistent with the MIGRATION_OBJ
macro name.

This will make future conversion to OBJECT_DECLARE* easier.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Tested-By: Roman Bolshakov <r.bolshakov@yadro.com>
Message-Id: <20200825192110.3528606-51-ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>