xen/swiotlb: Remove functions not needed anymore.

Sparse warns us off:
drivers/xen/swiotlb-xen.c:506:1: warning: symbol 'xen_swiotlb_map_sg' was not declared. Should it be static?
drivers/xen/swiotlb-xen.c:534:1: warning: symbol 'xen_swiotlb_unmap_sg' was not declared. Should it be static?

and it looks like we do not need this function at all.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/swiotlb-xen.c

@@ -466,14 +466,6 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 }
 EXPORT_SYMBOL_GPL(xen_swiotlb_map_sg_attrs);
 
-int
-xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
-		   enum dma_data_direction dir)
-{
-	return xen_swiotlb_map_sg_attrs(hwdev, sgl, nelems, dir, NULL);
-}
-EXPORT_SYMBOL_GPL(xen_swiotlb_map_sg);
-
 /*
  * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
  * concerning calls here are the same as for swiotlb_unmap_page() above.
@@ -494,14 +486,6 @@ xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 }
 EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg_attrs);
 
-void
-xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
-		     enum dma_data_direction dir)
-{
-	return xen_swiotlb_unmap_sg_attrs(hwdev, sgl, nelems, dir, NULL);
-}
-EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg);
-
 /*
  * Make physical memory consistent for a set of streaming mode DMA translations
  * after a transfer.

include/xen/swiotlb-xen.h

@@ -23,15 +23,6 @@ extern dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 extern void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
 				   size_t size, enum dma_data_direction dir,
 				   struct dma_attrs *attrs);
-/*
-extern int
-xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sg, int nents,
-		   enum dma_data_direction dir);
-
-extern void
-xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sg, int nents,
-		     enum dma_data_direction dir);
-*/
 extern int
 xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 			 int nelems, enum dma_data_direction dir,