dmaengine: ioatdma: workaround SKX ioatdma version

The Skylake ioatdma is technically CBDMA 3.2+ and contains the same hardware
bits with some additional 3.3 features, but it's not really 3.3 where the
driver is concerned.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>