alpha: use iommu_is_span_boundary helper function

iommu_is_span_boundary in lib/iommu-helper.c was exported for PARISC IOMMUs
(commit 3715863aa142c4f4c5208f5f3e5e9bac06006d2f).  Alpha's IOMMU can use it.

This removes the check on the boundary size alignment because
iommu_is_span_boundary does.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Richard Henderson <rth@twiddle.net>
Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 002703b..729cdbd 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -330,6 +330,9 @@
 config PCI_SYSCALL
 	def_bool PCI
 
+config IOMMU_HELPER
+	def_bool PCI
+
 config ALPHA_CORE_AGP
 	bool
 	depends on ALPHA_GENERIC || ALPHA_TITAN || ALPHA_MARVEL