dmaengine: fsl: remove bad channel update

dmaengine: fsl: remove bad channel update

Commit 6f8c8f93f075 ("dmaengine: fsl: convert tasklets to use new
tasklet_setup() API") broke this driver by not removing the old channel
update method.

Fix this by remove the offending call as channel is queried from
tasklet structure.

Fixes: 6f8c8f93f075 ("dmaengine: fsl: convert tasklets to use new tasklet_setup() API")
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20201001164740.178977-1-vkoul@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>