[IA64] avoid unnecessarily SWIOTLB bounce buffering

x86 improved range_straddles_page_boundary() by the c/s 501:5486a234923d.
The same discussion applies to ia64. This patch is ia64 counter part of it.

[ported from mainline version]
Signed-off-by: Alex Williamson <alex.williamson@xxxxxx>
linux-2.6.18-xen changeset: ec6e3e18ea314e9520ee6bba898e30228bf3bda4
linux-2.6.18-xen date: Wed Apr 02 10:02:57 2008 -0600

diff -r cdca34378e8e linux-2.6-xen-sparse/arch/i386/kernel/pci-dma-xen.c
--- a/linux-2.6-xen-sparse/arch/i386/kernel/pci-dma-xen.c	Mon Mar 31 18:09:19 2008 +0100
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/pci-dma-xen.c	Wed Apr 02 21:00:10 2008 -0600
@@ -74,6 +74,11 @@ do {							\
 		BUG();					\
 	}						\
 } while (0)
+
+#ifdef __ia64__
+#undef pfn_to_mfn
+#define pfn_to_mfn pfn_to_mfn_for_dma
+#endif
 
 static int check_pages_physically_contiguous(unsigned long pfn, 
 					     unsigned int offset,
diff -r cdca34378e8e linux-2.6-xen-sparse/include/asm-ia64/dma-mapping.h
--- a/linux-2.6-xen-sparse/include/asm-ia64/dma-mapping.h	Mon Mar 31 18:09:19 2008 +0100
+++ b/linux-2.6-xen-sparse/include/asm-ia64/dma-mapping.h	Wed Apr 02 21:00:10 2008 -0600
@@ -124,13 +124,7 @@ address_needs_mapping(struct device *hwd
 	return (addr & ~mask) != 0;
 }
 
-static inline int
-range_straddles_page_boundary(void *p, size_t size)
-{
-	extern unsigned long *contiguous_bitmap;
-	return (((((unsigned long)p & ~PAGE_MASK) + size) > PAGE_SIZE) &&
-	        !test_bit(__pa(p) >> PAGE_SHIFT, contiguous_bitmap));
-}
+extern int range_straddles_page_boundary(paddr_t p, size_t size);
 #endif
 
 #endif /* _ASM_IA64_DMA_MAPPING_H */