ASoC: Intel: avs: Fix route override

Instead of overriding existing memory strings that may be too short,
just allocate needed memory and point the route at it.

Reported-by: Jason Montleon <jmontleo@redhat.com>
Link: https://github.com/thesofproject/avs-topology-xml/issues/22#issuecomment-2127892605
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Link: https://lore.kernel.org/r/20240603102818.36165-3-amadeuszx.slawinski@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>