[IA64] SN specific version of dma_get_required_mask()

Create a platform specific version of dma_get_required_mask()
for ia64 SN Altix. All SN Altix platforms support 64 bit DMA
addressing regardless of the size of system memory.
Create an ia64 machvec for dma_get_required_mask, with the
SN version unconditionally returning DMA_64BIT_MASK.

Signed-off-by: John Keller <jpk@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/include/asm/dma-mapping.h b/arch/ia64/include/asm/dma-mapping.h
index bbab7e2..1f912d9 100644
--- a/arch/ia64/include/asm/dma-mapping.h
+++ b/arch/ia64/include/asm/dma-mapping.h
@@ -9,6 +9,8 @@
 #include <linux/scatterlist.h>
 #include <asm/swiotlb.h>
 
+#define ARCH_HAS_DMA_GET_REQUIRED_MASK
+
 struct dma_mapping_ops {
 	int             (*mapping_error)(struct device *dev,
 					 dma_addr_t dma_addr);