ASoC: SOF: ipc4-pcm: Use consistent name for snd_sof_pcm_stream pointer

ASoC: SOF: ipc4-pcm: Use consistent name for snd_sof_pcm_stream pointer

Throughout the file the pointer for snd_sof_pcm_stream is named either
'stream' or (wrongly) 'spcm' which confuses the reader.

Use 'sps' for the pointer name as it is the most common name used in SOF
codebase.

Signed-off-by: Peter Ujfalusi <[email protected]>
Reviewed-by: Pierre-Louis Bossart <[email protected]>
Reviewed-by: Ranjani Sridharan <[email protected]>
Link: https://msgid.link/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>