ioat1: trim ioat_dma_desc_sw

Save 4 bytes per software descriptor by transmitting tx_cnt in an unused
portion of the hardware descriptor.

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dma/ioat/hw.h b/drivers/dma/ioat/hw.h
index e13f3ed4..7481fb1 100644
--- a/drivers/dma/ioat/hw.h
+++ b/drivers/dma/ioat/hw.h
@@ -63,7 +63,11 @@
 	uint64_t	next;
 	uint64_t	rsv1;
 	uint64_t	rsv2;
-	uint64_t	user1;
+	/* store some driver data in an unused portion of the descriptor */
+	union {
+		uint64_t	user1;
+		uint64_t	tx_cnt;
+	};
 	uint64_t	user2;
 };
 #endif