soundwire: slave: fix scanf format

fix cppcheck warning:

[drivers/soundwire/slave.c:145]: (warning) %x in format string (no. 1)
requires 'unsigned int *' but the argument type is 'signed int *'.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191022233147.17268-1-pierre-louis.bossart@linux.intel.com


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