ASoC: SOF: sof-audio: Treat tplg_ops->route_setup() as optional

Other topology ops have been treated as optional, including the route_free.

Handle the route_setup in a conforming way as optional callback.
Note: we do not have checks for the callbacks itself which makes them all
optional in practice.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Link: https://lore.kernel.org/r/20221221102328.9635-2-peter.ujfalusi@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>