ASoC: SOF: ipc: retain DSP context after FW exception.

Add config option to prevent DSP entering D3 after any FW exception.
This can then be used to dump FW context for debug.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190927200538.660-5-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>