ASoC: cs35l56: Use DAPM widget for firmware PLAY/PAUSE

If we use a DAPM widget instead of mute_stream() to send the
PLAY command we can issue the plays to multiple amps in parallel.
With mute_stream each codec driver instance is called one at a
time so we get N * PS0 delay time.

DAPM does each stage on every widget in a card before moving to
the next stage. So all amps will do the PRE_PMU then all will do
the POST_PMU. The PLAY is sent in the PRE_PMU so that they all
power-up in parallel. After the PS0 wait in the first POST_PMU
all the other amps will also be ready so there won't be any extra
delay, or it will be negligible.

There's also no point waiting for the MBOX ack in the PRE_PMU.
We won't see a PS0 state in POST_PMU if it didn't ack the PLAY
command. So we can save a little extra time.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230411152528.329803-3-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>