powerpc: Use sg->dma_length in sg_dma_len() macro on 32-bit

Currently, the 32-bit code uses sg->length instead of sg->dma_lentgh
to report sg_dma_len.  However, since the default dma code for 32-bit
(the dma_direct case) sets dma_length and length to the same thing,
we should be able to use dma_length there as well.  This gets rid of
some 32-vs-64-bit ifdefs, and is needed by the swiotlb code which
actually distinguishes between dma_length and length.
Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/scatterlist.h

@@ -21,7 +21,7 @@ struct scatterlist {
 	unsigned int offset;
 	unsigned int length;
 
-	/* For TCE support */
+	/* For TCE or SWIOTLB support */
 	dma_addr_t dma_address;
 	u32 dma_length;
 };
@@ -34,11 +34,7 @@ struct scatterlist {
  * is 0.
  */
 #define sg_dma_address(sg)	((sg)->dma_address)
-#ifdef __powerpc64__
 #define sg_dma_len(sg)		((sg)->dma_length)
-#else
-#define sg_dma_len(sg)		((sg)->length)
-#endif
 
 #ifdef __powerpc64__
 #define ISA_DMA_THRESHOLD	(~0UL)