ASoC: SOF: topology: allocate string for tuples

In preparation to handle tuples from multiple topologies, duplicate the
tuple string value by allocating memory for it.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Liam Girdwood <liam.r.girdwood@intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://patch.msgid.link/20250414063239.85200-2-yung-chuan.liao@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>