ioat: preserve chanctrl bits when re-arming interrupts

The register write in ioat_dma_cleanup_tasklet is unfortunate in two
ways:
1/ It clears the extra 'enable' bits that we set at alloc_chan_resources time
2/ It gives the impression that it disables interrupts when it is in
   fact re-arming interrupts

[ Impact: fix, persist the value of the chanctrl register when re-arming ]

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/registers.h b/drivers/dma/ioat/registers.h
index a83c733..4380f6f 100644
--- a/drivers/dma/ioat/registers.h
+++ b/drivers/dma/ioat/registers.h
@@ -75,7 +75,11 @@
 #define IOAT_CHANCTRL_ERR_INT_EN		0x0010
 #define IOAT_CHANCTRL_ANY_ERR_ABORT_EN		0x0008
 #define IOAT_CHANCTRL_ERR_COMPLETION_EN		0x0004
-#define IOAT_CHANCTRL_INT_DISABLE		0x0001
+#define IOAT_CHANCTRL_INT_REARM			0x0001
+#define IOAT_CHANCTRL_RUN			(IOAT_CHANCTRL_INT_REARM |\
+						 IOAT_CHANCTRL_ERR_COMPLETION_EN |\
+						 IOAT_CHANCTRL_ANY_ERR_ABORT_EN |\
+						 IOAT_CHANCTRL_ERR_INT_EN)
 
 #define IOAT_DMA_COMP_OFFSET			0x02	/* 16-bit DMA channel compatibility */
 #define IOAT_DMA_COMP_V1			0x0001	/* Compatibility with DMA version 1 */