soundwire: export sdw_update() and sdw_update_no_pm()

We currently export sdw_read() and sdw_write() but the sdw_update()
and sdw_update_no_pm() are currently available only to the bus
code. This was missed in an earlier contribution.

Export both functions so that codec drivers can perform
read-modify-write operations without duplicating the code.

Fixes: b04c975e ('soundwire: bus: use sdw_update_no_pm when initializing a device')
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Bard Liao <bard.liao@intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Acked-By: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20210614180815.153711-2-pierre-louis.bossart@linux.intel.com


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