ASoC: SOF: append extended data to sof_ipc_comp_mixer

Append the extended data to the end of the struct sof_ipc_comp_mixer,
construct the ipc for COMP_NEW during the topology load stage.

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20200904132744.1699575-9-kai.vehmanen@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>