ioat3: dca and raid operations are incompatible

RAID operations cause a system hang on platforms with DCA
(Direct-Cache-Access) enabled.  So turn off RAID capabilities in this
case.

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

drivers/dma/ioat/hw.h

@@ -39,6 +39,8 @@
 #define IOAT_VER_3_0            0x30    /* Version 3.0 */
 #define IOAT_VER_3_2            0x32    /* Version 3.2 */
 
+int system_has_dca_enabled(struct pci_dev *pdev);
+
 struct ioat_dma_descriptor {
 	uint32_t	size;
 	union {