ASoC: SOF: ipc4-topology: restore gateway config length

The initial code had a logic flaw where the gateway config length kept
increasing after each playback/capture trigger, with the DMA config
TLV being added at every call of sof_ipc4_prepare_copier_module()

This didn't cause any issues with regular playback/capture, but this
was flagged as an error by firmware in the case of multiple amplifiers
on different links.

Fixes: a0659f81 ("ASoC: SOF: ipc4-topology: add DMA config TLV to IPC data")
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20230807210959.506849-5-pierre-louis.bossart@linux.intel.com


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