soundwire: intel: introduce helper for link synchronization

After arming the synchronization, the SYNCGO field controls the
hardware-based synchronization between links.

Move the programming and wait for clear of SYNCGO to dedicated helper.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200716150947.22119-5-yung-chuan.liao@linux.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>