soundwire: stream: group sdw_stream_ functions

Group all exported functions prior to split of add in alloc/config
stages necessary for support of multiple calls to hw_params() by
ALSA/ASoC core.

Pure code move, no functionality change.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20220126011715.28204-14-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>