ASoC: soc-pcm: improve BE transition for PAUSE_RELEASE

ASoC: soc-pcm: improve BE transition for PAUSE_RELEASE

Commit 3aa1e96a2b95 ("ASoC: soc-pcm: fix BE handling of PAUSE_RELEASE")
did not modify the existing logic and kept the same logic for the following
transition

    play FE1    -> BE state is START
    pause FE1   -> BE state is PAUSED
    play FE2    -> BE state is START
    stop FE2    -> BE state is STOP <<< !!
    release FE1 -> BE state is START
    stop FE1    -> BE state is STOP

At the time it was identified by reviewers that a better solution
might consist in

    play FE1    -> BE state is START
    pause FE1   -> BE state is PAUSED
    play FE2    -> BE state is START
    stop FE2    -> BE state is PAUSE <<< !!
    release FE1 -> BE state is START
    stop FE1    -> BE state is STOP

This patch suggest a transition to PAUSE when all the 'active' streams
are paused. This would allow for a more consistent resource management
for platforms where PAUSE and STOP are handled differently.

To track the special case of an FE going from PAUSE_PUSH to STOP, we
add a state variable for each FE context. This 'fe_pause' boolean is
set on PAUSE_PUSH and cleared on either PAUSE_RELEASE and STOP
triggers.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20220406190056.233481-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>