soundwire: cadence_master: add hw_reset capability in debugfs

Provide debugfs capability to kick link and devices into hard-reset
(as defined by MIPI). This capability is really useful when some
devices are no longer responsive and/or to check the software handling
of resynchronization.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191022235448.17586-3-pierre-louis.bossart@linux.intel.com


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