ASoC: SOF: Refactor rx function for fuzzing

Refactor the function so reading the data is done outside the work
function so fuzzing can pass data directly into the work callbacks.

Also expose the inner function outside the module so we can call it from
the injector.

Signed-off-by: Curtis Malainey <cujomalainey@chromium.org>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20230608221822.2825786-1-cujomalainey@chromium.org


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