hw: apply accel compat properties without touching globals

hw: apply accel compat properties without touching globals

Instead of registering compat properties as globals, let's keep them
in their own array, to avoid mixing with user globals.

Introduce object_apply_global_props() function, to apply compatibility
properties from a GPtrArray.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>