ENGR00231773-4 ASRC: use scatter list and stall bit for asrc convert

ENGR00231773-4 ASRC: use scatter list and stall bit for asrc convert

In the origin code, ASRC driver use cyclic way to process DMA task
transfering data to/from ASRC input/output FIFO. In this case, it is
necessary that user application should promise that the input buffer
flow is continuous. If not, there would be 0 data be inserted into data
flow. The output data would be noisy.

In this patch,
	1 use scatter list instead of cyclic SDMA: with scatter list,
SDMA would stop when the applied scatter list nents are finished.
	2 set stall bit for ASRC "memory->ASRC->memory" convert to stop
ASRC convert when input data is not send into ASRC input FIFO in time.

Signed-off-by: Chen Liangjun <b36089@freescale.com>