[IA64] Add DMA_ERROR_CODE define.

This piggybacks on git commit 8fd524b3
("x86: Kill bad_dma_address variable") wherein we use now the
dma_map_ops->mapping_error to check for errors and the standard
check is against DMA_ERROR_CODE. Introduce it to the IA64 world.

CC: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
CC: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/include/asm/dma-mapping.h

@@ -12,6 +12,8 @@
 
 #define ARCH_HAS_DMA_GET_REQUIRED_MASK
 
+#define DMA_ERROR_CODE 0
+
 extern struct dma_map_ops *dma_ops;
 extern struct ia64_machine_vector ia64_mv;
 extern void set_iommu_machvec(void);