ioatdma: Fix bug in selftest after removal of DMA_MEMSET.

Commit 48a9db46 (3.11) removed the memset op in the xor selftest for ioatdma.
The issue is that with the removal of that op, it never replaced the memset
with a CPU memset. The memory being operated on is expected to be zeroes but
was not. This is causing the xor selftest to fail.

Cc: <stable@vger.kernel.org>
Signed-off-by: NDave Jiang <dave.jiang@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dma/ioat/dma_v3.c

@@ -1376,6 +1376,8 @@ static int ioat_xor_val_self_test(struct ioatdma_device *device)
 		goto free_resources;
 	}
 
+	memset(page_address(dest), 0, PAGE_SIZE);
+
 	/* test for non-zero parity sum */
 	op = IOAT_OP_XOR_VAL;