dmaengine: ioatdma: add error strings to chanerr output

Provide a mechanism to translate CHANERR bits to English strings in order
to allow user to report more concise errors.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>