soundwire: Add missing EXPORT for sdw_slave_type

soundwire: Add missing EXPORT for sdw_slave_type

include/sdw_type.h provides the function is_sdw_slave() which
requires sdw_slave_type. But sdw_slave_type was not exported.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://patch.msgid.link/20260112140758.215799-2-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>