ASoC: generic-dmaengine-pcm: Set BATCH flag when residue reporting is not supported

For dmaengine drivers which do not support transfer residue reporting we update
the PCM pointer with period granularity. Set the SNDRV_PCM_INFO_BATCH flag in
this case to let userspace know about this.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>