dmaengine: imx-dma: remove 'imxdma_setup_sg_hw' function.

Removing this function allows moving 'ccr_to_device' and
'ccr_from_device' from internal struct to channel struct.
This repesents a step forward towards removing auxiliary
'internal' structure.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>