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>