ASoC: topology: Fix potential build issues with undeclared structs

We should be declaring snd_kcontrol_new and soc_dai_link as both are
used within this header so need to be declared.

[Reworded commit message to indicate this wasn't an immediate build
failure -- broonie]
Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

include/sound/soc-topology.h

@@ -28,6 +28,8 @@ struct snd_soc_component;
 struct snd_soc_tplg_pcm_fe;
 struct snd_soc_dapm_context;
 struct snd_soc_card;
+struct snd_kcontrol_new;
+struct snd_soc_dai_link;
 
 /* object scan be loaded and unloaded in groups with identfying indexes */
 #define SND_SOC_TPLG_INDEX_ALL	0	/* ID that matches all FW objects */