soundwire: add flag to ignore all command/control for mockup devices

SoundWire mockup devices don't take part in the command/control
protocol, so all commands will complete with -ENODATA or
Command_Ignored results. With a flag, we can suppress such errors in
the bus management and make it appear as if all read/writes succeed.

Signed-off-by: Pierre-Louis Bossart <[e-mail]>
Reviewed-by: Rander Wang <[e-mail]>
Signed-off-by: Bard Liao <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

include/linux/soundwire/sdw.h

···
  * initialized
  * @first_interrupt_done: status flag tracking if the interrupt handling
  * for a Slave happens for the first time after enumeration
+ * @is_mockup_device: status flag used to squelch errors in the command/control
+ * protocol for SoundWire mockup devices
  */
 struct sdw_slave {
 	struct sdw_slave_id id;
···
 	struct completion initialization_complete;
 	u32 unattach_request;
 	bool first_interrupt_done;
+	bool is_mockup_device;
 };
 
 #define dev_to_sdw_dev(_dev) container_of(_dev, struct sdw_slave, dev)

sound/soc/codecs/sdw-mockup.c

···
 	dev_set_drvdata(dev, sdw_mockup);
 	sdw_mockup->slave = slave;
 
+	slave->is_mockup_device = true;
+
 	ret =  devm_snd_soc_register_component(dev,
 					       &snd_soc_sdw_mockup_component,
 					       sdw_mockup_dai,