ASoC: SOF: pcm: move the check for prepared flag

ASoC: SOF: pcm: move the check for prepared flag

Move the check for the prepared flag inside snd_pcm_dsp_pcm_free() to
avoid having to check it before every invocation of the function.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20211125101520.291581-8-kai.vehmanen@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>