soundwire: bus: provide correct return value on error

It seems to be a typo. It makes more sense to return the return value
of sdw_update() instead of the value we want to update.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200227220949.4013-1-pierre-louis.bossart@linux.intel.com


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