soundwire: remove master data port properties

The SoundWire and DisCo specifications do not define Master data ports
or related properties. Data ports are only defined for Slave devices,
so remove the unused member in properties.

Credits: this patch is based on an earlier internal contribution by
Vinod Koul, Sanyog Kale, Shreyas Nc and Hardik Shah.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>