ASoC: fix pxa2xx-pcm.h path

Since pxa2xx-pcm.h is removed from sound/soc/pxa, we need to update the
path in related files.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Tested-by: Ian Lartey <ian@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>