ASoC: SOF: sof-client: Introduce sof_client_dev_entry structure

Introduce a new internal structure for wrapping the sof_client_dev and
move members away from the client visible struct that they must not
access, let alone see (sdev and the list).

The changes are mechanical in nature and contained within sof-client core
code, no functional change or change in behavior is introduced.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Message-ID: <20250829102510.15159-3-peter.ujfalusi@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>