ASoC: SOF: Rename dtrace_is_supported flag to fw_trace_is_supported

ASoC: SOF: Rename dtrace_is_supported flag to fw_trace_is_supported

Rename the internal flag to not limit it's use for dma-trace, but to be
used for generic firmware tracing functionality.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220516104711.26115-3-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>