iommu: export iommu_area_reserve helper function

x86 has set_bit_string() that does the exact same thing that
set_bit_area() in lib/iommu-helper.c does.

This patch exports set_bit_area() in lib/iommu-helper.c as
iommu_area_reserve(), converts GART, Calgary, and AMD IOMMU to use it.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 6f7b974..70537d1 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -572,7 +572,7 @@
 	if (start_page + pages > last_page)
 		pages = last_page - start_page;
 
-	set_bit_string(dom->bitmap, start_page, pages);
+	iommu_area_reserve(dom->bitmap, start_page, pages);
 }
 
 static void dma_ops_free_pagetable(struct dma_ops_domain *dma_dom)
diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
index fe7695e..080d1d2 100644
--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -261,7 +261,7 @@
 			       badbit, tbl, start_addr, npages);
 	}
 
-	set_bit_string(tbl->it_map, index, npages);
+	iommu_area_reserve(tbl->it_map, index, npages);
 
 	spin_unlock_irqrestore(&tbl->it_lock, flags);
 }
diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index 508ef47..3dcb1ad 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -827,7 +827,7 @@
 	 * Out of IOMMU space handling.
 	 * Reserve some invalid pages at the beginning of the GART.
 	 */
-	set_bit_string(iommu_gart_bitmap, 0, EMERGENCY_PAGES);
+	iommu_area_reserve(iommu_gart_bitmap, 0, EMERGENCY_PAGES);
 
 	agp_memory_reserved = iommu_size;
 	printk(KERN_INFO