ASoC: topology: Only free TLV for volume mixers of a widget

This patch will check the type of embedded controls for a widget, and
only free the TLV of volume mixers. Bytes controls don't have TLV.

Just free the private value which is used as struct soc_mixer_control
for volume mixers or soc_bytes_ext for bytes controls. No need to cast
to these types before freeing it.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>