Add .prepare and .hw_free callback to dailink.

The companion patch for this patch is the removal of stream operations
in the .prepare and .hw_free callbacks at the DAI level in
drivers/soundwire/intel.c
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200904182854.3944-4-yung-chuan.liao@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>