regmap: sdw-mbq: Don't assume the regmap device is the SoundWire slave

regmap: sdw-mbq: Don't assume the regmap device is the SoundWire slave

Currently, the code assumes that the device that registered the
MBQ register map is the actual SoundWire slave device. This works
fine for all current users, however future SDCA devices will
likely be implemented with the SoundWire slave as a parent device
and separate child drivers with regmaps for each audio Function.
Update the regmap_init_sdw_mbq_cfg macro to allow these two
to be specified separately.

Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Link: https://patch.msgid.link/20251020155512.353774-3-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>