dmaengine: ioat: Decreasing allocation chunk size 2M->512K

requreing kmalloc of 2M high chance to fail in
fragmented memory.
IOAT ring requires 64k * 64B memory
which will be achived by 512k * 8 allocation
instead of 2M * 2.

Acked-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Leonid Ravich <Leonid.Ravich@emc.com>
Link: https://lore.kernel.org/r/20200416170628.16196-2-leonid.ravich@dell.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/ioat/dma.h

@@ -83,7 +83,7 @@ struct ioatdma_device {
 
 #define IOAT_MAX_ORDER 16
 #define IOAT_MAX_DESCS (1 << IOAT_MAX_ORDER)
-#define IOAT_CHUNK_SIZE (SZ_2M)
+#define IOAT_CHUNK_SIZE (SZ_512K)
 #define IOAT_DESCS_PER_CHUNK (IOAT_CHUNK_SIZE / IOAT_DESC_SZ)
 
 struct ioat_descs {