ASoC: SOF: Intel: hda-loader: clear the IPC ack bit after FW_PURGE done

Set DONE bit after the FW_PURGE IPC is polled successfully, to clear the
interrupt and avoid the arrival of the confusing unexpected ipc.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Link: https://lore.kernel.org/r/20200228231850.9226-4-pierre-louis.bossart@linux.intel.com


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