ioat: Remove duplicated devm_kzalloc() calls for ioatdma_device

The memory for ioatdma_device structure is being allocated in
alloc_ioatdma()

Signed-off-by: Minskey Guo <chaohong_guo@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>