ASoC: SOF: loader: add dynamic debug trace

We currently have no trace referring to the firmware path, add a trace
to help debug cases where the wrong file might be used.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200107160840.1524-3-pierre-louis.bossart@linux.intel.com


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