ASoC: SOF: ipc4-topology: Initialize in_format to NULL in sof_ipc4_get_audio_fmt

ASoC: SOF: ipc4-topology: Initialize in_format to NULL in sof_ipc4_get_audio_fmt

If the available_fmt->num_input_formats is 0 and there is a failure during
the output format parsing then a kfree() would be called on the
uninitialized in_format pointer.

By initializing the in_format to NULL, this error can be avoided.

Fixes: 7ab6b1e8302c ("ASoC: SOF: ipc4-topology: Modify the type of available input/output formats")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20230317063524.8280-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>