ASoC: atmel: mchp-pdmc: Skip ALSA restoration if substream runtime is uninitialized

ASoC: atmel: mchp-pdmc: Skip ALSA restoration if substream runtime is uninitialized

[ Upstream commit 09cfc6a532d249a51d3af5022d37ebbe9c3d31f6 ]

Update the driver to prevent alsa-restore.service from failing when
reading data from /var/lib/alsa/asound.state at boot. Ensure that the
restoration of ALSA mixer configurations is skipped if substream->runtime
is NULL.

Fixes: 50291652af52 ("ASoC: atmel: mchp-pdmc: add PDMC driver")
Signed-off-by: Andrei Simion <andrei.simion@microchip.com>
Link: https://patch.msgid.link/20240924081237.50046-1-andrei.simion@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>