dmaengine: mv_xor_v2: remove interrupt coalescing

The current implementation of interrupt coalescing doesn't work, because
it doesn't configure the coalescing timer, which is needed to make sure
we get an interrupt at some point.

As a fix for stable, we simply remove the interrupt coalescing
functionality. It will be re-introduced properly in a future commit.

Fixes: 19a340b1 ("dmaengine: mv_xor_v2: new driver")
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>