ALSA: pxa2xx: Use managed PCM buffer allocation

ALSA: pxa2xx: Use managed PCM buffer allocation

Now with the recent addition of WC buffer allocation support, we can
use the standard PCM buffer allocation helpers for pxa2xx drivers.
This allows us to remove lots of superfluous code.

Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210802072815.13551-6-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>