soundwire: bus: add enumerated Slave device to device list

soundwire: bus: add enumerated Slave device to device list

Currently Slave devices are only added on startup, either from Device
Tree or ACPI entries. However Slave devices that are physically
present on the bus, but not described in platform firmware, will never
be added to the device list. The user/integrator can only know the
list of devices by looking a dynamic debug logs.

This patch suggests adding a Slave device even if there is no matching
DT or ACPI entry, so that we can see this in sysfs entry.

Initial code from Srinivas. Comments, fixes for ACPI probe and edits
of commit message by Pierre.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Co-developed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200924194430.121058-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>