soundwire: qcom: check of_property_read status

Cppcheck complains:

drivers/soundwire/qcom.c:773:6: style: Variable 'ret' is assigned a
value that is never used. [unreadVariable]
 ret = of_property_read_u8_array(np, "qcom,ports-block-pack-mode",
     ^

The return value is checked for all other cases, not sure why it was
missed here.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20210302091122.13952-10-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>