LF-4536: dmaengine: fsl-edma-v3: fix coverity issue

Fix Coverity Issue:17611886 Uninitialized scalar variable, though
DEV_TO_DEV case never care residue of current transfer by calling
dmaengine_tx_status.

Signed-off-by: Robin Gong <yibin.gong@nxp.com>
Reviewed-by: Shengjiu Wang <shengjiu.wang@nxp.com>