soundwire: sysfs: remove sdw_slave_sysfs_init()

Now that sdw_slave_sysfs_init() only calls sdw_slave_sysfs_dpn_init(),
just do that instead and remove sdw_slave_sysfs_init() to get it out of
the way to save a bit of logic and code size.

Cc: Vinod Koul <vkoul@kernel.org>
Cc: Bard Liao <yung-chuan.liao@linux.intel.com>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: Sanyog Kale <sanyog.r.kale@intel.com>
Cc: alsa-devel@alsa-project.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-By: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Link: https://lore.kernel.org/r/2024013030-denatured-swaddling-b047@gregkh


Signed-off-by: Vinod Koul <vkoul@kernel.org>