soundwire: Provide build stubs for common functions

Provide stub functions when CONFIG_SOUNDWIRE is not set for functions
that are quite likely to be used from common code on devices supporting
multiple control buses.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20221125142028.1118618-3-ckeepax@opensource.cirrus.com


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