Use the generic dmaengine PCM driver instead of a custom implemention.  There is
a minor functional change, the ux500 PCM driver did not preallocate the audio
buffer, while the generic dmaengine PCM driver will do this.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>