Since the soc generic dmaengine pcm driver allows using the defualt settings,
so the pcm->config maybe NULL.
Signed-off-by: NXiubo Li <Li.Xiubo@freescale.com>
Acked-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NMark Brown <broonie@linaro.org>