ASoC: soc.h: dobj is used only when SND_SOC_TOPOLOGY

snd_soc_dobj is used only when SND_SOC_TOPOLOGY was selected.
Let's enable it under SND_SOC_TOPOLOGY.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/87o8xq251d.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>