fixup_tplg_name() doesn't need to keep the string, allocated for
filename - it's temporary.

Inspired by similar change for hda:
commit b9088535 ("ASoC: SOF: Intel: HDA: don't keep a temporary variable")
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220715145216.277003-8-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>