ASoC: SOF: Add clarifying comments for sof_core_debug and DSP dump flags

Update the comment for the global SOF level debug flags and add one for
the flags used to control the DSP dump functionality.

Document the expected behavior when the SOF_DBG_DUMP_OPTIONAL is passed
for the DSP dump:
Only print the dump if SOF_DBG_PRINT_ALL_DUMPS is set
Print must use KERN_DEBUG log level

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Chao Song <chao.song@intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20211223113628.18582-19-peter.ujfalusi@linux.intel.com


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