ASoC: amd: ps: update dev index value in irq handler

Instead of using hard coded index value for platform device index,
retrieve the device index based on platform devices created.
In PDM config case, ACP PCI driver retrieves dev index from
pdm_dev_index variable.
This will avoid overhead when multiple endpoint combinations
support is added later.
platform device index will vary based on audio endpoint
configuration.

Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Link: https://lore.kernel.org/r/20221221172855.1618766-3-Vijendar.Mukunda@amd.com
Signed-off-by: Mark Brown <broonie@kernel.org>