ASoC: SOF: Use sof_debug_check_flag() instead of sof_core_debug directly

The sof_debug_check_flag() is available for checking flags set in
sof_core_debug.

sof_core_debug can be marked static in core.c

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20211223113628.18582-5-peter.ujfalusi@linux.intel.com


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