dmaengine: imx-dma: remove data member from internal structure.

Internal structure is just an auxiliary structure used for the initial
merge which is meant to be gone. As data member is not use anywhere
we can simply remove it.

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>