AMD IOMMU: __unmap_single: check for bad_dma_address instead of 0

Impact: minor fix
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/kernel/amd_iommu.c

@@ -983,7 +983,8 @@ static void __unmap_single(struct amd_iommu *iommu,
 	dma_addr_t i, start;
 	unsigned int pages;
 
-	if ((dma_addr == 0) || (dma_addr + size > dma_dom->aperture_size))
+	if ((dma_addr == bad_dma_address) ||
+	    (dma_addr + size > dma_dom->aperture_size))
 		return;
 
 	pages = iommu_num_pages(dma_addr, size, PAGE_SIZE);