ASoC: cs35l56: Skip first init_completion wait in dsp_work if init_done

At the start of dsp_work() only wait for init_completion if !init_done.
This allows system suspend to re-queue dsp_work() without having to
do a dummy complete() of init_completion.

A dummy completion in system suspend would have to be conditional on
init_done. But that would create a possible race condition between our
system resume and cs35l56_init() in the corner case that we suspend right
after the SoundWire core has enumerated and reported ATTACHED.

It is safer and simpler to have cs35l56_init() as the only place that
init_completion is completed, and dsp_work() as the only place that
it is consumed.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230411152528.329803-4-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>