ASoC: xtensa: Remove unnecessary snd_pcm_lib_preallocate_free_for_all()

The ALSA core takes care that all preallocated memory is freed
when the PCM itself is freed. There is no need to do this
manually in the driver.

Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>