ASoC: SOF: Protect swidget->use_count with mutex for kcontrol access race

The use_count of the swidget is protect by ALSA core PCM locking with the
exception when an associated kcontrol is changed.

It has been observed that a rightly timed kcontrol access during stream
stop can result of an attempt to send a control update to a widget which
has been freed up between the check of the use_count and the message
sending.

We need to protect the entire sof_widget_setup() and sof_widget_free()
execution to make it safe to rely on the use_count.
Move the code under an _unlocked() function and use a mutex to protect
the execution of the functions for concurrency.
On the control path we need to use the lock only for the kcontrol access,
the widget_kcontrol_setup() op is called with the lock already held.

Reported-by: Guennadi Liakhovetski <[email protected]>
Signed-off-by: Peter Ujfalusi <[email protected]>
Reviewed-by: Pierre-Louis Bossart <[email protected]>
Reviewed-by: Ranjani Sridharan <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

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