ASoC: xtensa: Use managed buffer allocation

Clean up the driver with the new managed buffer allocation API.
The superfluous snd_pcm_lib_malloc_pages() and
snd_pcm_lib_free_pages() calls are dropped.

Cc: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20191210142614.19405-17-tiwai@suse.de


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