swiotlb: use iommu_is_span_boundary helper function

iommu_is_span_boundary in lib/iommu-helper.c was exported for PARISC IOMMUs
(commit 3715863aa142c4f4c5208f5f3e5e9bac06006d2f).  SWIOTLB can use it instead
of the homegrown function.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a12dbb2..1d9d874 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -537,9 +537,6 @@
 	  Calgary anyway, pass 'iommu=calgary' on the kernel command line.
 	  If unsure, say Y.
 
-config IOMMU_HELPER
-	def_bool (CALGARY_IOMMU || GART_IOMMU)
-
 # need this always selected by IOMMU for the VIA workaround
 config SWIOTLB
 	bool
@@ -550,6 +547,8 @@
 	  access 32-bits of memory can be used on systems with more than
 	  3 GB of memory. If unsure, say Y.
 
+config IOMMU_HELPER
+	def_bool (CALGARY_IOMMU || GART_IOMMU || SWIOTLB)
 
 config NR_CPUS
 	int "Maximum number of CPUs (2-255)"