[POWERPC] Remove the global dma_direct_offset

We no longer need the global dma_direct_offset, update the comment to
reflect the new reality.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/dma_64.c

@@ -112,10 +112,11 @@ EXPORT_SYMBOL(dma_iommu_ops);
 /*
  * Generic direct DMA implementation
  *
- * This implementation supports a global offset that can be applied if
- * the address at which memory is visible to devices is not 0.
+ * This implementation supports a per-device offset that can be applied if
+ * the address at which memory is visible to devices is not 0. Platform code
+ * can set archdata.dma_data to an unsigned long holding the offset. By
+ * default the offset is zero.
  */
-unsigned long dma_direct_offset;
 
 static unsigned long get_dma_direct_offset(struct device *dev)
 {

include/asm-powerpc/dma-mapping.h

@@ -189,8 +189,6 @@ static inline void dma_unmap_sg(struct device *dev, struct scatterlist *sg,
 extern struct dma_mapping_ops dma_iommu_ops;
 extern struct dma_mapping_ops dma_direct_ops;
 
-extern unsigned long dma_direct_offset;
-
 #else /* CONFIG_PPC64 */
 
 #define dma_supported(dev, mask)	(1)