soundwire: mipi_disco: fix master/link error

The MIPI DisCo specification for SoundWire defines the
"mipi-sdw-link-N-subproperties" for slaves and
"mipi-sdw-master-N-subproperties" for controllers. This is a mistake
that was not identified until now.

Existing Intel DSDT tables use 'link' everywhere, and the MIPI spec
will be updated to deprecate "mipi-sdw-master-N-subproperties"

Fix to parse firmware information on existing devices. If we ever see
a system with 'master-N-subproperties' I guess we'll have to try both.

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