ASoC: amd: ps: fix byte count return value for invalid SoundWire manager instance

acp_get_byte_count() function should return zero bytes instead of
-EINVAL for invalid SoundWire manager instance.

Fixes: f7229173 ("ASoC: amd: ps: add SoundWire dma driver dma ops")
Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Link: https://lore.kernel.org/r/20230626105356.2580125-5-Vijendar.Mukunda@amd.com


Signed-off-by: Mark Brown <broonie@kernel.org>