alpha: fix iommu-related boot panic

This fixes a boot panic due to a typo in the recent iommu patchset from
FUJITA Tomonori <tomof@acm.org> - the code used dma_get_max_seg_size()
instead of dma_get_seg_boundary().

It also removes a couple of unnecessary BUG_ON() and ALIGN() macros.

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Reported-and-tested-by: Bob Tracy <rct@frus.com>
Acked-by: FUJITA Tomonori <tomof@acm.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/kernel/pci_iommu.c

@@ -144,15 +144,14 @@ iommu_arena_find_pages(struct device *dev, struct pci_iommu_arena *arena,
 	unsigned long base;
 	unsigned long boundary_size;
 
-	BUG_ON(arena->dma_base & ~PAGE_MASK);
 	base = arena->dma_base >> PAGE_SHIFT;
-	if (dev)
-		boundary_size = ALIGN(dma_get_max_seg_size(dev) + 1, PAGE_SIZE)
-			>> PAGE_SHIFT;
-	else
-		boundary_size = ALIGN(1UL << 32, PAGE_SIZE) >> PAGE_SHIFT;
-
-	BUG_ON(!is_power_of_2(boundary_size));
+	if (dev) {
+		boundary_size = dma_get_seg_boundary(dev) + 1;
+		BUG_ON(!is_power_of_2(boundary_size));
+		boundary_size >>= PAGE_SHIFT;
+	} else {
+		boundary_size = 1UL << (32 - PAGE_SHIFT);
+	}
 
 	/* Search forward for the first mask-aligned sequence of N free ptes */
 	ptes = arena->ptes;