x86/amd-iommu: Fix possible integer overflow

commit d91afd15 upstream.

The variable i in this function could be increased to over
2**32 which would result in an integer overflow when using
int. Fix it by changing i to unsigned long.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/x86/kernel/amd_iommu.c

@@ -540,7 +540,7 @@ static void flush_all_devices_for_iommu(struct amd_iommu *iommu)
 static void flush_devices_by_domain(struct protection_domain *domain)
 {
 	struct amd_iommu *iommu;
-	int i;
+	unsigned long i;
 
 	for (i = 0; i <= amd_iommu_last_bdf; ++i) {
 		if ((domain == NULL && amd_iommu_pd_table[i] == NULL) ||