soundwire: slave: don't init debugfs on device registration error

[ Upstream commit 8893ab5e8ee5d7c12e0fc1dca4a309475064473d ]

The error handling flow seems incorrect, there is no reason to try and
add debugfs support if the device registration did not
succeed. Return on error.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Link: https://lore.kernel.org/r/20200419185117.4233-2-yung-chuan.liao@linux.intel.com


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