fix xen_swiotlb_dma_mmap prototype

BugLink: http://bugs.launchpad.net/bugs/1721550

xen_swiotlb_dma_mmap was backported from v4.10, but older
kernels before commit 00085f1e ("dma-mapping: use unsigned long
for dma_attrs") use a different signature:

arm/xen/mm.c:202:10: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
  .mmap = xen_swiotlb_dma_mmap,
          ^~~~~~~~~~~~~~~~~~~~
arm/xen/mm.c:202:10: note: (near initialization for 'xen_swiotlb_dma_ops.mmap')

This adapts the patch to the old calling conventions.

Fixes: "swiotlb-xen: implement xen_swiotlb_dma_mmap callback"
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/xen/swiotlb-xen.c

@@ -689,7 +689,7 @@ EXPORT_SYMBOL_GPL(xen_swiotlb_set_dma_mask);
 int
 xen_swiotlb_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 		     void *cpu_addr, dma_addr_t dma_addr, size_t size,
-		     unsigned long attrs)
+		     struct dma_attrs *attrs)
 {
 #if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
 	if (__generic_dma_ops(dev)->mmap)

include/xen/swiotlb-xen.h

@@ -62,5 +62,5 @@ xen_swiotlb_set_dma_mask(struct device *dev, u64 dma_mask);
 extern int
 xen_swiotlb_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 		     void *cpu_addr, dma_addr_t dma_addr, size_t size,
-		     unsigned long attrs);
+		     struct dma_attrs *attrs);
 #endif /* __LINUX_SWIOTLB_XEN_H */